Is a website database created automatically?

Using BuddyPress, I’m going to build an experimental Social Network.

A few minutes ago I was starting to build the Social Network, when I realized that maybe it could not work properly without its main component: a Database.

As far as I know, social networks such as Facebook, Twitter, Tumblr (and so on) have a huge database behind where every data (personal infos, passwords, emails, pictures, videos, etc.) are saved allowing the user to see them in his/her profile.

Now the question is: how can I make my Social Network work properly? Is there a WordPress plugin that create this required Database, or is everything included in the BuddyPress pack?