Here are the data structures with brief descriptions:

CBucket
CMMG5_Bezier
CMMG5_dNode	Cell for linked list of double value
CMMG5_dNode_s
CMMG5_Edge	Structure to store edges of a MMG mesh
CMMG5_Hash	Identic as MMG5_HGeom but use MMG5_hedge to store edges instead of MMG5_hgeom (memory economy)
CMMG5_hedge	Used to hash edges (memory economy compared to MMG5_hgeom)
CMMG5_hgeom	Cell of the hash table of geom edges
CMMG5_HGeom	Hash table to store geometric edges
CMMG5_Info	Store input parameters of the run
CMMG5_iNode	Cell for linked list of integer value
CMMG5_iNode_s
CMMG5_Mat	To store user-defined references in the mesh (useful in LS mode)
CMMG5_Mesh	MMG mesh structure
CMMG5_Par
CMMG5_Point	Structure to store points of a MMG mesh
CMMG5_Prism
CMMG5_Quad
CMMG5_Sol
CMMG5_sol	MMG Solution structure (for solution or metric)
CMMG5_Tetra
CMMG5_Tria
CMMG5_xPoint	Structure to store surface points of a MMG mesh
CMMG5_xPrism	Structure to store the surface prism of a MMG mesh
CMMG5_xTetra	Structure to store the surface tetrahedra of a MMG mesh
Cmytime	Chrono object
Csqueue