I suppose in a very general sense a HomeGroup/Workgroup could be loosely defined as a peer network, but only in so far as there is not a server (As in Microsoft Active Directory Domain Controller) in place overseeing network resources and security and all network nodes are basically equal. But truly it is still more like a client server environment in that each node determines what they are sharing and who has access to those resources.
A true peer to peer network is really more like some of the common file sharing programs like (Napster, ShareBear, Morpheus, LimeWire, uTorrent, etc.,) where the program establishes the sharing, and exposes those shares as "Seeds" to other computers running the same program, and makes them generally available to any and all other clients on the network. Other examples of peer to peer networking might be something like SETI@home or Folding@home where a portion of your computers resources (processing power and memory) are utilized by third party programs to help in efforts to search for extraterrestrial intelligence or to understand protein folding and its' relationship to some diseases.
HomeGroup/WorkGroup networking is really much more secure in that it basically only involves computers on your (usually private) subnet. While most of the other examples or peer to peer networking involves sharing files and or system resources with other internet connected computers.
Hope this helps.
Yes, your information was enlightening to me although I am just above an average user. I learned concepts that I was unaware of and have a much clearer view of the similarities and differences.
The one concept that I liked to read was that I am secure within my own network.
Thank you very much for the very educational response.