4 templates come with the download already built in
The marketplace tab is... a marketplace for tested themes and add-ons...both free and paid for. Google searches will also show other resources for Concrete5

Please read the documentation area (tab on top right of this page) to get a basic overview of what Concrete5 is.
It is a Very rewarding and versatile CMS and I think you'll enjoy the ease and flexibility.

Welcome to the community and Enjoy :)