The interview at Amazon works as follows. You'll be contacted at some point by a recruiter and you'll go over some general stuff. If you don't say anything disqualifying, they'll schedule a phone screen for you. If this is for a technical position, the phone screen will involve some problem solving, some coding, and maybe even some design work.
Following that first phone screen, if you pass (sometimes even if you didn't) you'll be asked to go though a second phone screen. If you do well on this, then you'll be asked to fly out to Seattle for an in person interview. Let me first say that the phone screen questions are far easier than the questions you'll be asked in person, so don't get a false sense of confidence.
Amazon.com will fly you out to Seattle on their dime and put you up in a very nice room in a nice hotel.
On the day of your interview you sit in a room with a white board as 5-7 people rotate through the room giving you 45minute to 1 hour interview sessions. There will be very few behavioral questions, it will most likely be dominated by coding on a white board.
The people that interview you will then confer, usually within a day or two, and make a decision as to whether Amazon will extend an offer. The whole process usually moved fairly quickly.