Location of postgresql database on OS X?

I'm sure this has been answered but I cannot seem to find an answer.

I installed postgresql using Homebrew (brew install postgresql) which installed to /usr/local/Cellar/postgresql. Afterwords per the instructions I did this:

If this is your first install, create a database with:
    initdb /usr/local/var/postgres

As I understand it, initdb creates a new cluster of databases. So when I did the above is "postgres" the database name and the database itself or just all the necessary bits that all postgresql databases will need?

Where does the actual database end up living? I am new to postgresql and looking for a file or binary that is the database. So, where is the database, and when I create a new one where does it go?