First of all, the hiring manager called you to have the phone interview. He/she asked you some technical questions and your past working projects. If your background is matching what they are looking for the candidate, then HR will arrange the on-site interview immediately. The on-site interview is a whole day interview from 9am to 5pm. You may have one-to-one and small group interview, even they may ask you a lot of technical questions during lunch time. Don't be surprise! At the end of the interview, the hiring manager get all the feedbacks from the team. Then the hiring manager let you know the decision as soon as possible. It possibly takes fews days to hear back from the hiring manager.