A daemon is a Linux program that run in the background, just
like a 'Service' on Windows. It can perform all sorts of tasks
that do not require direct user input. Apache is a daemon, so
is MySQL. All you ever hear from them is found in somewhere in
/var/log, yet they silently power over 40%
of the Internet.
You reading this page, would not have been possible without them.
So clearly: a daemon is a powerful thing, and can be bend to do a
lot of different tasks.