Index files are files that are used to manage the files on your computer by searching and Cataloging the files so that they can be found quickly and easily.
Usually the index files are to be found with the system files, though there can be differances with the files showing in the documents folder.
Windows, Linux, Unix and Mac OS X all support Index files.
» Operating System
How to open .index files?
Software to open .index files
What are .index files