I don't "get" Facebook

So, for my course in social media, I've created a Facebook account to try and understand what it's all about. Uploaded a picture, tried to make sure there's nothing personal on there, figured out how to get my name in the web address (a text message - really? Do people actually find Facebook user-friendly?), friended my husband, who I'm pretty sure was my friend anyway, and now...what?  It seems I'm supposed to 1) troll around for friends 2) post something 3) link to something 4) like something.  I'm not getting what the basic activity is here.  I guess social networks make more sense to people who are actually sociable.  Oops.