UNIX systems use scripts to control “daemons” which provide “services” (for example your sound output) to run a UNIX system. UNIX systems consist of a variety of services (daemons).
A “daemon” is a system process which runs in the background (zero interaction) performing a particular task.
Daemons normally have a “d” on the end of their name and either listen for certain events or perform a system task, for example sshd listens for secure shell requests to the particular machine and handles them when they occur.
Daemons usually perform critical system tasks such as control swap-space, memory management and various other tasks.