Please describe a stack and the two operations it performs.

When the Amazon interviewer asks you to describe something, you should immediately identify the question as being technical. When responding to a technical question, you first define the term or concept and then describe how it is used in the work you are performing. If the interviewer asks you follow-up questions, they are expressing a strong interest in this topic and indicating that it is important to their operations. This is a signal for you to expand on your answer and give them more details than you normally would.