SILIS means: SImple LogIn System. You can use SILIS in you website. It's an complete package with everything what's needed.
Everything what you need to now is: how php works, the rest is detailed in the php files.
There isn't that much information on this page but yeah, you don't need to now so much at this moment.
Do you need some help with SILIS? Then go to: The GitHub Page and op an issue or read the wiki.