Daemon refers to a software program that keeps running in the background and exists to handle periodic service requests. The requests that this software runs are expected by the computer system it operates under. What the daemon program is that it forwards these requests to the appropriate programs (or processes). 

The server of pages on the Web each has what is called a Hypertext Transfer Protocol Daemon, or simply HTTPD. The HTTPD constantly waits for the generated requests that come from Web clients and the users of these clients.

It must be noted however that the program, Daemon is different from another program called, demon. Daemon is the program that operates on its own under the operating system, and demon is just a facet of a larger application program.