Here are the classes, structs, unions and interfaces with brief descriptions:

[detail level 1234]

Feel	[marker1]
detail
BoundaryCondition	Brief description
Environment	Initialize, finalize, and query the Feel++ environment
NAME	Brief description
dyna
Jacobi	1D Jacobi polynomial
Feel
detail
AdFuncPow	Brief description
fem
CrouzeixRaviart	CrouzeixRaviart Finite Element
Hermite	Hermite polynomial set
Lagrange	Lagrange polynomial set
Nedelec	Nedelec Finite Element
RaviartThomas	RaviartThomas Finite Element
math
Constant	Structure that holds a constant with different numerical representation
vf
details
Projector	Base class for projectors
AboutData	Holds information needed by the "About" box and other classes
AboutPerson
ADExpr	Brief description
ADType	Automatically Diffentiated Numerical Type
Advection
AdvReact	Advection-Reaction solver
Air	Air material
Aitken	Aitken relaxation method for fixed point iterations
Application	Information about the Application
ApplicationXML	XML application
AssertContext	Details about a failed assertion
Backend	Base class for all linear algebra backends
BackendEigen
BareEdge	The Edge basis class It contains the attributes common to all Edges In particular, it contains the two size_type's (first and second) of the points at the two ends of the edge
BareFace	The base Face class
BareItemsHandler	Bare Items Handler
BarePoint	The Point basis class It contains the attributes common to all Points In particular, it contains the one size_type's (first) of the point
Basis	Base class for basis
Bdf	Backward differencing formula time discretization
BFGSInvHessian
BoundaryAdapted	BoundaryAdapted Basis on simplex
BoundingBox	Bounding box for a matrix of points
CastIron	Cast iron material
cmpBareItem
cmpBareItem< BareEdge >	< The actual comparison operator
cmpBareItem< BareFace >
cmpBareItem< BarePoint >	< The actual comparison operator
Component
Context	Context class
Continuous	Describe continuous functions
Convex	Convex base class
core_data
CRB	Certifed Reduced Basis class
CRBApp	Certified Reduced Basis application
CRBDB	Brief description
CRBModel	Certified Reduced Basis Model class
CRBModelTrilinear	Certified Reduced Basis Model trilinear class
CRBSCM	SCM algorithm
CRBTrilinear	Certifed Reduced Basis for Trilinear forms class
DAR
DataMap	Data layout in a multi-processor environnement
DirScalingMatrix	Implements the directional Scaling Matrix for directionally-scaled trust region
DiscontinuousInterfaces	Describes discontinuous interfaces and provide dof creation
Dof	Class that represents a degree of freedom
DofComposite	Compositing of degree of freedom table
DofTable	Local-to-global Degree of Freedom table
DualBasis	Basis of a space P' dual of some space P
Dubiner	Dubiner polynomial orthonormal basis
dummy_data	Dummy data type
EIM	Empirical interpolation of a function to obtain an affine decomposition
Elaxi
equalities	Define the equalities type
ErrorBase
Example	Brief description of the class Example
Exporter	Export Feel generated data to some file formatsUse the visitor and factory pattern
ExporterEnsight	Exporter to Ensight format
ExporterEnsightGold	Exporter to EnsightGold format
ExporterExodus	Exporter to Exodus format
ExporterGmsh	Exporter to GMSH format
ExporterGnuplot	Exporter to GNUPLOT format
ExporterQuick	Simple interface to exporter
ExprBase	Base class for expression
Factory	Implements a generic object Factory
FactoryClone	Implements a generic cloning object Factory
FactoryDefaultError
FilterFromVtk
FilterFromVtk3D
FiniteElement	Finite element following Ciarlet framework
Functional	Linear functional
functional	Defines the functional type
ComponentPointEvaluation	Generate the functional associated with a point evaluation associated with a component
ComponentsPointsEvaluation	Generate the functionals associated with point set
DirectionalComponentPointEvaluation	Functional associate with directional component point evaluation
DirectionalComponentPointsEvaluation	Functional associate with directional component point evaluation
IntegralMoment	Functional that returns $\ell_u (v) = \int_\Omega( u\, v )$
IntegralMomentOfDerivative	Functional that returns $\ell_u^i (v) = \int_\Omega( \frac{d u}{d x_i} \, v )$
IntegralMomentOfDivergence	Functional that returns $\ell_u^i (v) = \int_\Omega( \frac{d u}{d x_i} \, v )$
IntegralMomentOnFace	Functional that returns $\ell_u (v) = \int_{\Gamma} ( u\, v )$ where $\Gamma \subset \partial \Omega$
IntegralMomentsOnFace	Functional that returns $\ell_u (v) = \int_{\Gamma} ( u\, v )$ where $\Gamma \subset \partial \Omega$
PointDerivative	Generate the functional associated with a point derivative
PointEvaluation	Generate the functional associated with a point evaluation
PointsDerivative	Generate the functionals associated with point set
PointsEvaluation	Generate the functionals associated with point set
PointsGradient	Generate the functionals associated with point set
FunctionalSet	Set of functionals
FunctionSpace
FunctionSpaceBase	Brief description
Gauss	Gauss quadrature points
GaussLobatto	Gauss quadrature points
Geo0D
GeoElement0D
GeoElement1D	Class for 1D elements
GeoElement2D	Class for 2D elements
GeoElement3D	Class for 3D elements
GeoEntity	Base class for all geometric entities
reference_convex
GeoMap	Structure for the geometrical mapping
Context
Inverse
GeoMapInverse	Handles the geometric inversion for a given (supposedly quite large) set of points
GeoND	Base class for Multi-dimensional basis Geometrical Entities
Gmsh	Gmsh Mesh Generator
GmshEllipsoidDomain	N-Ellipsoid Domain description for gmsh mesh generation
GmshHypercubeDomain	Tensorized Domain description for gmsh mesh generation
GmshSimplexDomain	Simplex Domain description for gmsh mesh generation
GraphCSR	Graph representation of the Compressed Sparse Row format
Ground	Heating and Cooling of the ground due to surface temperature
HeatSink
IMExact	Exact integration method
IMGeneral	Integration method interface class
Importer
ImporterGmsh	Gmsh importer class
IMTetrahedra< 1, T >
inequalities	Define the inequalities type
Info	Information provider for versioning and installation directories
IntegrationDegree
Iteration	Brief description
Jacobi	1D Jacobi polynomial
JacobiDegree
KDTree	KDTree class
Laplacian
LaplacianLM
Legendre	Legendre polynomial orthonormal basis
LU
Material	Material base class
MaterialLib	Material library
matrix_node
MatrixBlock	Block of matrices
MatrixBlockBase	!
MatrixEigenDense	Interface to eigen sparse matrix
MatrixEigenSparse	Interface to eigen sparse matrix
MatrixShell	Matrices that define its action against a vector
MatrixShellSparse	Allow all sparse matrices to be shell matrices
MatrixSparse
MatrixTriplet	Brief description
MatrixUBlas	Interface to ublas sparse matrix
MatrixValue	Interface to matrix
Mesh	Unifying mesh class
Mesh0D	0D mesh class
Mesh1D	1D mesh class
Mesh2D	2D mesh class
Mesh3D	3D mesh class
MeshBase	Base mesh class
MeshHighOrder
MeshMover	Move mesh according to a given map
MeshTraits	Traits for meshes
Mortar	Brief description
node
NoPeriodicity	NoPeriodicity class holder
Normalized
Operator	Operator between function spaces
OperatorInterpolation	Global interpolation operator
OperatorLagrangeP1
OperatorLinear	Linear Operator between function spaces, represented by a matrix
OperatorLinearFree	Linear Operator Free between function spaces, represented by a matrix but this matrix is not automatically assembled
OperatorLinearParametrized	An interface for linear parametrized operators
OperatorSteklovPc	OperatorSteklovPc made easy
OperatorTrace	OperatorTrace made easy
OpusApp	Certified Reduced Basis application
OpusAppEigs	Opus application
OrthogonalPolynomialSet	Set of orthogonal polynomials over a convex
OseenDefaults	Oseen Default Data
Output	Output class to describe code outputs
Parameter	Parameter class to describe code inputs
ParameterSpace	Parameter space class
Element	Element of a parameter space
Sampling	Parameter space sampling class
Partitioner
Periodic	Periodic class holder
PeriodicStokes
PFemApp	Parametrized Finite Element Method Application
POD	POD class
PointSet	Class of all PointSet on a Convex
PointSetFekete
PointSetInterpolation	Good interpolation point sets on a convex
PointSetQuadrature	Quadrature point set base class
PointSetToMesh	Transform a point set to a mesh data structure using a Delaunay
PolicyCreationUsingNew
PolicyFeelTimeDefault
Polynomial	Polynomial class
PolynomialSet	Set of polynomials
Preconditioner	Base class for preconditioner
PreconditionerPetsc	Petsc preconditioner class
Principal	Principal modified functions
problem	Optimization problem specifications
value	Compute the value of the functionals, equalities and inequalities associated with the problem
Projector	Projection made easy
PsLogger
RankUp
Reference	Reference convex
RegionMarker2
RegionMarker3
RegionMarkre
RegionProcess
RegionTree	Implements a region-tree for point search in a set of boxes
ResistanceLaplacian
Scalar
Simget	Simulation Object
Simplex	Simplex of dimension `Dim`
Singleton	Implement the Singleton pattern
SolverBase	Abstract base class for wrapped (linear) solvers
SolverConstrained
COptions	Holds the options for the SolverConstrained
Stats	Holds the statistics for SolverConstrained
SolverEigen	Base class for eigen solvers
SolverLinear
SolverNonLinear	Non linear solver base interface
SolverUMFPACK	Interface for the UMFPACK Solver
SolverUnconstrained
COptions	Parameters for the solver
Stats	Statistics holder for the solver
Sound
Sphere
Stokes	Solves the stokes equations
StorageUBlas
StructuredGrid	Class to represent a Structured Grid
SubMeshData	Data structure storing sub mesh data
Surface
SVD	Singular Value Decomposition of a rectangular matrix
System	System of PDE associated to a function space
SystemExplicit	Describes an explicit system
SystemImplicit	Describes an implicit system
SystemImplicitLinear	Brief description
SystemImplicitNonLinear	Describes nonlinear implicit systems
Tensor2
Tensor3
TensorisedBoundaryAdapted	TensorisedBoundaryAdapted Basis on simplex products
ThermalFin
TimerMap	Timers map
TimeSet	Data TimeSet
Step	Step in a time set
TypeInfo	Wrapper for std::type_info
Vector
VectorBlock	Block of vector
VectorEigen	Interface to vector
Vectorial
VectorUblas	Interface to vector
VectorValue	Interface to vector
Visitor
VisitorBase	The base class of any Acyclic Visitor
VisitorBaseImpl	Implements non-strict visitation (you can implement only part of the Visit functions)
VisitorCyclic
Convection
ConvectionCrb
Diode
IMSimplex	Brief description
Laplacian
Laplacian_parabolic
LShape
MortarLaplacian
ResidualEstimator
steady_edp	Defines the edp to be solved in the stationnary case : $- nu*\Delta u = f$
ThreeFieldsLaplacian
transient_edp	Defines the edp to be solved in the instationnary case : $dfrac{\partial u}{\partial t} - nu*\Delta u = f$