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

FileGDBAPI::ByteArray	A utility class for working with database BLOBs
FileGDBAPI::EnumRows	An enumerator of rows. Used as a return type for table queries
FileGDBAPI::Envelope	Defines an XY spatial extent
FileGDBAPI::FieldInfo	A utility class for providing field information
FileGDBAPI::Geodatabase	A class representing a File Geodatabase
FileGDBAPI::MultiPartShapeBuffer	MultiPart Shape Buffer accessor functions
FileGDBAPI::MultiPatchShapeBuffer	MultiPatch Shape Buffer accessor functions
FileGDBAPI::MultiPointShapeBuffer	MultiPoint Shape Buffer accessor functions
FileGDBAPI::PointShapeBuffer	Point Shape Buffer accessor functions
FileGDBAPI::Row	Provides methods to get and set data on table rows
FileGDBAPI::ShapeBuffer	A utility class for working with serialized shapes
FileGDBAPI::Table	Provides methods to work with tables, such as querying and modifying both schema and data