P2P is a network method in contrast with the general client-server method of using a server and having each PC connect to that server. The terminals in P2P networks (peers) are general PCs, which are often called "nodes" whether they are servers or notebooks. The terminals connect with other terminals to exchange information or to share information by responding to requests from other terminals.
The term "P2P" became well-known thanks to file sharing software, but in recent years it is attracting attention in the field of virtual currencies.
Bitcoin exchanges data on a P2P basis. So, there is no specific administrator in place and its operations are stable. However, this makes it difficult to ensure the integrity of data.
Bitcoin was groundbreaking in that it used a mechanism called a "blockchain" to maintain this integrity.