These are common types of annotations (tates) but this list is not exhaustive.

A good annotation can contain one or several of the following:

• Sample identification
• Artist explanation
• Reaction
• Reference or allusion identification
• Slang decoding
• Wordplay decoding
• Themes
• Relevant image
• Joke
• Producer tag

Translation related:
• Lyric translation
• Annotation translation

Lyrics related:
• Alternate lyrics
• Uncertain lyrics

Misc:
• Question
• Something creative!
Non-lyric annotations:

• Verse header
• Produced By
• Instrumental breaks and solos
• Cover art