What is a client and server? 

Client-server model is a traditional approach, a disputed application structure where the client sends request to server and it responses back to client with the requested information.  The sever host runs one or more server programs and regular data backup is required. 

As we can see in the picture, clients could be local PCs, mobiles, laptops, printers which connect to server(s) on the same network. The purpose of this is to share the resources across the network. In this way, it could increase the efficiency and effectiveness of the business and information could be collected on a timely basis.    

Reference: Picture from Automation mission