You can mark some journals and submissions as "viewable by friends only" I believe, so if ya got a big vent or rant to post, you can do it under that. :3

You can be friends with someone without following them, and vice versa.

Following someone lets you know when they post stuff; friending someone doesn't do that.

Friending someone lets you choose who can send you PMs or shouts, if you want, but by default anyone can.

I was wandering the same thing. Good to know!

Friends follow you. Followers don't friend you owo. >3