Quick context: If you were sent this link, it came from this blog post.
Note: YC highly discourages founders to overprepare and recite answers for the interview. Instead, use this list of questions to think through your business and be able to explain your business in clear terms.
What is your company working on?
Why did you pick this idea to work on? Do you have domain expertise in this area? How do you know people need what you're making?
Who are your competitors? What do you understand about your business that they don't?
How do or will you make money? How much could you make?
What does each founder do on the team?
Why did you choose this idea? What have you learned so far from working on it?
How large is the market that you are going after?
What part of your project are you going to build first?
Who needs what you’re making?
How do you know they need it? Why is this a problem for them?
What are they doing now?