The autoload directory is for standard Vim autoload scripts.

These are functions used by plugins and for general use.  They will be loaded
automatically when the function is invoked.  See ":help autoload".

gzip.vim	for editing compressed files
netrw*.vim	browsing (remote) directories and editing remote files
tar.vim		browsing tar files
zip.vim		browsing zip files
paste.vim	common code for mswin.vim and menu.vim
spellfile.vim	downloading of a missing spell file

Omni completion files:
ccomplete.vim		C
csscomplete.vim		HTML / CSS
htmlcomplete.vim	HTML
javascriptcomplete.vim  Javascript
phpcomplete.vim		PHP
pythoncomplete.vim	Python
rubycomplete.vim	Ruby
syntaxcomplete.vim	from syntax highlighting
xmlcomplete.vim		XML (uses files in the xml directory)