45 minute interview with a lower-level manager -- largely behavioral "tell me about a time" questions; asked a question regarding your biggest accomplishment so far, which can be pretty difficult to answer as a 21 year-old.... -- a couple business-related questions to analyze applicable retail skills

Mostly fit/behavioral questions that help them better determine if your skills, and more importantly goals, align with the company's goals. Amazon strongly highlights long term growth and customer retention as an important factor rather than simply maximizing revenue. If at the end of the interview, you feel like you clicked with the company (and your interviewer), it's probably a good sign. If you noticed that you had to mentally adjust some of your answers to better fit the company more so than usual, then Amazon's probably not the best company for you.