Okey, I wanna build a social network for my webpage... I am not going to earn money on it or something, and I hosts the website free on a server. So I dont need capital for it, like everyone tells me. It is just for a smaller group of people than the world. So I have searched all around the internet but cant find anything that really learns me and explains me how I am going to do it by scratch.
Like w3schools do for html!?
Is there anyone who knows how, or knows where I can learn it like the way I want it? (Free?)

What exactly do you want? A forum maybe?

Daniel - There are MANY options available for you, here's one I found by Googling 'social network scripts open source'... http://www.socialgo.com/?gclid=CPbH2t2ilqsCFYIBQAodYUNjzQ#a_aid=4be9814159d95&a_bid=485126a0&chan=ust1sscr

I can't vouch for it (or any others, although I had played around with one a few years ago). My suggestion, is to check a few of them out and find one that fits your needs.

http://buddypress.org/

Building a social network from scratch is going to take months of learning PHP/MySQL.

i suggest you to try some discussion forum first, so that you can get some idea to manage it some how.
http://www.youtube.com/watch?v=oofzJGxNd7Q