Hi Michael, difficult to say what they're talking about with more specifics. "Peer to Peer" is a vague term without some context. Who's the supplier? What's the use case?
The keywords I see in your question is "remote accessing setup." This makes me think maybe they're talking about using something much like "Log Me In" so they (or you) can remotely access their NVRs and use that for "setup." I think a few of the integrators here on IPVM use something like this to do remote maintenance on customers' VMS systems.
If that's not the context, then they could be talking about P2P networking technology that uses internet servers to broker a P2P connection between the server (in this case the NVR) and a client so video streaming need not reflect through a cloud-based media server but rather can be direct from the server to client. A familiar example would be Skype. This technology can be complex, is really cool, sometimes very effective, but can have reliablity and consistency problems.
As you may have noticed today Ethan published this piece on remote access to surveillance networks: Remote Network Access for Video Surveillance Guide
Some of the embedded NVR's/DVR's have created ways to reach the recorder from a remote device (phone) using technology that does not require DDNS or static IP's. The unit reports its path to a server with a unique identifier and the app then searches that server for a way to reach the recorder. Very similar to one of the methods deacribed in the article. When possible the device the. Opens a P2P connection and if not available the host provides a relay service.
Take a look at a similar discussion here and here. Now that Axis has implemented peer to peer in it's own cameras, this subject will call more attention.