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

[detail level 123]

▼NAssimp	Assimp's CPP-API and all internal APIs
CBaseImporter	FOR IMPORTER PLUGINS ONLY: The BaseImporter defines a common interface for all importer worker classes
CDefaultLogger	CPP-API: Primary logging facility of Assimp
▼CExporter	CPP-API: The Exporter class forms an C++ interface to the export functionality of the Open Asset Import Library
CExportFormatEntry	Internal description of an Assimp export format option
CImporter	CPP-API: The Importer class forms an C++ interface to the functionality of the Open Asset Import Library
CIOStream	CPP-API: Class to handle file I/O for C++
CIOSystem	CPP-API: Interface to the file system
CLogger	CPP-API: Abstract interface for logger implementations
CLogStream	CPP-API: Abstract interface for log stream implementations
CNullLogger	CPP-API: Empty logging implementation
CProgressHandler	CPP-API: Abstract interface for custom progress report receivers
CScopeGuard
CaiAnimMesh	NOT CURRENTLY IN USE
CaiBone	A single bone of a mesh
CaiCamera	Helper structure to describe a virtual camera
CaiColor3D	Represents a color in Red-Green-Blue space
CaiColor4t	Represents a color in Red-Green-Blue space including an alpha component
CaiExportDataBlob	Describes a blob of exported scene data
CaiExportFormatDesc	Describes an file format which Assimp can export to
CaiFace	A single face in a mesh, referring to multiple vertices
CaiFile	C-API: File callbacks
CaiFileIO	C-API: File system callbacks
CaiImporterDesc	Meta information about a particular importer
CaiLight	Helper structure to describe a light source
CaiLogStream	C-API: Represents a log stream
CaiMaterial	*/
CaiMatrix3x3t	Represents a row-major 3x3 matrix
CaiMatrix4x4t	Represents a row-major 4x4 matrix, use this for homogeneous coordinates
CaiMesh	A mesh represents a geometry or model with a single material
CaiPlane	Represents a plane in a three-dimensional, euclidean space
CaiPropertyStore	C-API: Represents an opaque set of settings to be used during importing
CaiQuaterniont	Represents a quaternion in a 4D vector
CaiRay	Represents a ray
CaiString	Represents an UTF-8 string, zero byte terminated
CaiTexel	Helper structure to represent a texel in a ARGB8888 format
CaiTexture	Helper structure to describe an embedded texture
CaiUVTransform	Defines how an UV channel is transformed
CaiVector2t	Represents a two-dimensional vector
CaiVector3t	Represents a three-dimensional vector
CaiVertexWeight	A single influence of a bone on a vertex