While answering this question you need to be honest. If you do not know enough about the project then politely address the basics. Remember they know much more about the technicalities than you don't try to fool them.
While answering this question make sure that you do enough research about the company and your job opening. It is imperative that you know about the job, its environment, technical aspects and possibly what type of projects you would be working with then do explain to him about all these.
State whether you are passionate about them and your contributions to the society. Also tell them whether you like to develop open source projects or proprietary projects and state the reason.
Project details, its uses and benefits, environment, team, client name?
You need to be as detailed as you can about these specific questions as they will decide your future job prospect and opportunity.
Technical interviews will test on your technical knowledge make sure that you are thorough with the basics and most of the companies ask you basics. If you do not know answer to a specific question tell them that you don't know the answer to that specific question it is no harm but if you try to attempt it with having knowledge it will have a catastrophic effect.