Qwest has an OC-12 optical cable backbone with more capacity than all of the backbones up to 1998. These NAPS are the hubs of the Internet. The NAP is somewhat like a train switching station where a train arrives at Kansas City and the first ten wagons are routed towards Chicago, the next five are sent to Dallas, and the last 7 are sent to Denver. NAPs route millions of bits per second. Thus there are hundreds of unofficial NAPs.
Backbones have access points in large cities.
They tap into the flow of information from the backbones and distribute to yet smaller customers, such as business and home subscribers. ATT WorldNet, when it started in 1996, was merely access to BBN Planet's network which in turn ran on MCI's backbone. The users paid ATT for the right to use BBN Planet. Some ISPs are regional, others are nationwide. Technically, not much.