This is basic BGDatabase API to use without CodeGeneration. Code Generation makes these API much easier to use, and we highly recommend to use it. More information about Code Generation is here

Name Class Description API link
Repository BGRepo The whole database, containing collection of metas(tables) and addons API
Meta (table) BGMetaEntity The database table, containing collection of fields (columns) and entities (rows) API
Field (column) BGField table's column API
Entity (row) BGEntity table's row API
Key BGKey key is a collection of fields for fast rows lookups
Index BGIndex index is a reference to a field for fast rows queries by this field values
Addon BGAddon each addon has its own API