Here are the data structures with brief descriptions:

mdb_copy
MDB_cursor	Opaque structure for navigating through a database
MDB_db
MDB_dbx
MDB_env	Opaque structure for a database environment
MDB_envinfo	Information about the environment
MDB_ID2
MDB_meta
MDB_metabuf
MDB_name
MDB_node
MDB_ntxn
MDB_page
MDB_pgstate
MDB_reader
MDB_rxbody
MDB_stat	Statistics for a database in the environment
MDB_txbody
MDB_txn	Opaque structure for a transaction handle
MDB_txninfo
MDB_val	Generic structure used for passing keys and data in and out of the database
MDB_xcursor