Well, you don't write what a character thinks or the reason for their actions in the actual text. The only things you write is what they do, and what they say. I like it because it has a visual element too. You can focus your energy on the writing, rather than having to describe every little detail about your character, like their clothing, or the surroundings, because that's already there.
It's a massive, open world that's constantly moving, so it feels... alive. Even if you're not there, things are still going to happen, which you'll then find out about when you come back to it. You get to RP with others through guilds of various ideals, like maybe a guardsmens guild, a noble house, a trading caravan, a band of cultists, whatever you want. You could also just go up and randomly chat with people. And some of the more community-orientated people on the servers actually host server-wide events that they themselves organize. Like a halloween dress-up party, with contests, prizes, mingling and stuff like that.
It would be difficult to get used to after being used to forum-RP'ing, though. It's alot more fast-paced, for sure. I know I had alot of difficulty with getting used to forum-RP'ing after WoW :P