The "Index" category is for lists and directories. It can overlap with other categories.
“A list of FanFics originally compiled by MC User The Count. Original thread can be found here...Master FanFic Index
“A list of names or nicknames of MC members. Feel free to add or remove yourself from the list.Nickname Index
“Beginning in late 2011, a member by the username of Muppetboy09 started to create his own smiles...Custom Smilies
“This page is a list of popular and noteable threads that do not deserve their own thread page...Notable Threads