Chess Rating

Is there anyone here who can Explain (at a grade 9 high school level) how the rating works on this site.

I am assuming there is a mathematical or computer forumla, is it public for us to see? or perhaps to complicated to understand.

Do the type of games you play (long, short, tournament) effect your rating or do we get a different rating for each?

I understand the general idea. Win - good, Loose - Bad

If I play against a Grand Master will I loose more points than if I play my 4 year old neice?

Just wondering.

http://www.chess.com/article/view/chess-ratings---how-they-work

A great help and interesting articles. Thank you for the link. I guess the only other variable is who you are playing against ( I might win more over one style of play than I would over another players form). But that is just being picky.