All iRacing subscriptions include 30 cars and 27 tracks(with over 83 unique track configurations).
If you click on this link and scroll to the bottom, you will see all the cars and tracks that come included with your initial iRacing Membership: http://www.iracing.com/membership/
For a more organized list, you can go to each link below:
https://www.iracing.com/tracks/
Click the filter to list only "Included with Membership" content 
We provide all of the cars and tracks needed to run the official Rookie series races.
Any additional tracks/cars will need to be licensed to your account.
If you have any additional questions, please email us at support@iracing.com.