This Facebook thing...I don't get it.

When I was at my parents over Christmas I met up with my two oldest friends, who still live in the general area down there. They keep in touch with other mostly through Facebook. Back in October P made an account for me on Fb but today was the first time I tried to use it, and I assume I'm doing something wrong, because I just don't get it. And for some reason, my secondary school doesn't exist. I assume I'll understand it sooner or later. Par for the course with me - I never did do twitter in the end, in spite of reading a 'how to' book in Smiths one afternoon. Perhaps I should have bought the book.