The server

• A server is a process (running program) that serves data for clients. Through metonymy, it can refer to a device used for running server programs.
• A server is a program that receives requests from clients and sends responses
• A client is a program that sends requests to servers and receives responses
• A server is just the role of the program or the computer which means if something acts like a server (receives requests and sends responses), then it is a server

Examples

• DNS server: a server that translates domain names into IP addresses

ONE SENTENCE SUMMARY:

A server is a running program or machine that provides services or resources to other programs or machines (called clients) over a network.