Video: "What is a Peer-to-Peer Network?" – Blockchain at Berkeley / Simply Explained (5 minutes) 

Link:

As you watch, note answers to these questions: 

• What is the main difference between client-server and P2P? 
• How does a P2P network stay running if nodes leave? 
• What happens to data in a P2P network if one node is corrupted? 
 

If the video link doesn't work: 

Alternative Video: "Blockchain 101 – A Visual Demo" by Anders Brownworth (first 7 minutes) 

Link :

or Search on YouTube:  "Peer to Peer Networks Explained Simply"