HR doesn't always provide accurate details. Many people end up feeling swindled. Get promises in writing and understand when you can use certain benefits (floating holidays, training budget, etc.).
Interview consists of a talk with a recruiter, a technical phone screen, then an in-person interview with 2 or 3 employees (at the same time). Each team has their own style of interviewing. If you are not a good fit for one team, they may pass you onto a team they think would be a better match.
There are no standard interview questions, so the interviews are mostly winged. Many times HR will not send your resume to the team until the day of, so interviewers don't usually have time to review your history.
Questions cover your background to see if you just click buttons, or if you know what's technically happening.
Tips:
If you don't know something,admit it. After an interview its common to hear 'He didn't know that much, but he was honest and enthusiastic. We can always train him"
Try to show your enthusiasm for the subject.
If you don't know the correct answer or give a guess, ask for the correct answer. It shows you care. If you get another interview somewhere else, you'll know the answer.
Dress to impress.