How does product of the day works?

If you have launched before, how does the product hunt of the day work? I thought it was whoever have more upvotes, but it's clearly not like that because I saw a product today that has close to 400 upvotes, and it's not even on the featured page nor the top 20; at the same time, I saw a product with less than half upvotes on the featured page and in the top 10. If you have any ideas, please help me understand that.