Generic handles are for playing NPCs, handles not yet approved, or for mimicking a source material handle.
Generics include: single punctuation, characters, and up to two combined punctuation/alt key/shift symbols (†~, o0, ?!, ‡= etc.), Mun names, descriptives including the mun name (example: Joe's NPC is...), or general descriptives (example: The Shadowy Figure in the Corner).
You can have up to six generic handles on your account (both because of limited availability and to prevent handle-hogging).
Private room advertising handles are handles which are used to promote an as-yet-unsupported private room.