In computer operating systems, a daemon is a computer program that runs as a background process, rather than being under the direct control of an interactive user. These help the kernel run important tasks such as sshd responsible for incoming connections, crond, responsible for tasks scheduled to be performed without a user present, or journald, which logs all of the services on a system.
The word daemon comes originally from Ancient Greece. Daemons typically were lesser deities which acted as spirit guides to mortals. The gods of Ancient Greece would use them as messengers. We could think of the kernel as god and the daemons as the messengers to the user. In fact, the Greek ángelos means “messenger”. This later influenced the Christian concept of angels. This gives a totally different perspective for the next time you run:
systemctl daemon-reload