By giving VCs small bits of info in a specific order (or close to it), they are able to start mentally checking things off of their list. Assuming the idea is sound, they need to see you have done your homework, and that you have a firm understanding of the market, the problem you are solving for that market, the competition in your way and the team who you're proposing can pull it off. Do these things, and you will have made it through the first step of the gauntlet.