ID
Anime
aid = short for anime ID
Every anime in the DB has exactly 1(!) unique ID.
Creq
cid = short for creq ID
Every creq in the DB has exactly 1(!) unique ID, which makes it possible to track down every change done.
Episode
eid = short for episode ID
Every episode in the DB has exactly 1(!) unique ID.
File
fid = short for file ID
Every file in the DB has exactly 1(!) unique ID.
Group
gid = short for group ID
Every group in the DB has exactly 1(!) unique ID.
Groups also have an agid = short for anime group id
This id is unique for each anime+group combination and is used for anime group ratings and other anime+group related stuff.
Producer
prid = short for producer ID
Every producer (company) in the DB has exactly 1(!) unique ID.
Review
rid = short for review ID
User
uid = short for user ID