I'm going to have an MRI next Wednesday. What can I expect?

I'm getting an MRI on my brain next Wednesday, because I have headaches all the frickin' time and I guess we're just making sure that I'm not a mutant and I don't have brain cancer or anything. I've never been in for an MRI or known anyone who has--what's it like? Is it that thing where they slide you into that capsule looking thing? I tried looking it up on the internet, but I only found a lot of jargon-laden medical explanations which really didn't help me at all. I'd like to hear from someone who's done this or knows someone who has.