installation on local host requires me to add a database. explain please.

[switchex]

Hello, i was finally able to install presta and get it to work on my local host ( my laptop) although i am not sure how i finally got it to work! anyway, i had a few questions please.

In step 3 (or was it 4?) of installation i was getting a message about not having a database (forgot exact wording of the message, sorry.. but it wasn't allowing me to complete registration) .. so i went to localhost/phpmyadmin/ and added a new DB (with just one field in it), and it worked like a charm! Can u please explain why i needed to add this DB? What does it do and why i need it?

thanks