You can collect them through other people who give you one. When you have enough badges, the "Llama" levels up (kinda). Some people are so die-hard they offer points for those who give them one. Lastly, you can use points to buy attachments for it.
They just...love llamas...these administrators. So, they started allowing the community to hand them out as well. It's interesting how much people love to get them just to have them get spiffier as you get more.
I thought after you got ten, they became super llamas with a cape....at least that's what happened to mine....it's another way of people saying like your stuff, like you....and it's harmless! Enjoy your llama..it doesn't cost to feed it, and it won't leave little messes all over your page!
It's basically a little pixel llama that sits on your profile page. You can give them to other people via the little give button in the top right of their profile pages. The more people who give you them the fancier your llama gets. So if ten people give you a llama you get an albino llama and so on. That's pretty much it. I have literally no idea why everyone went so crazy for them.
Well, dA has had that llama in the emoticons library thing for a long time. So I think $spyed felt them to be some kind of second mascot to fella. Well, they turned it into a badge and it's the only one that can be given for free. So, naturally it's become a huge sensation. There were a bunch of artworks and photos done with llamas as badges swelled in popularity. As you get more they change to different kinds of llamas too.