Data is the backbone of most web applications. It doesn't make sense to have an application that will dynamically and automatically update if there is no data for it to update with. While you can get content data from many sources including Twitter feeds like this week's inspiration post, the most common place to get and store data is in a database.
But if you've never managed a database before (and believe me, no one is born understanding normal forms and entity relationships) they can be pretty overwhelming. Luckily About.com has a Guide who can help. Mike Chapple has been the About.com Guide to Databases since 2000, and he makes it easy to get started building and using databases.