11.2 Understanding Ubuntu systemd Services
A service is essentially a process, typically running in the background, that provides specific functionality. The sshd service, for example, is the background process (also referred to as a daemon) that provides secure shell access to the system. Different systemd targets are configured to automatically launch different collections of services, depending on the functionality that is to be provided by that target.
Targets and services are types of systemd unit, a topic which will be covered later in this chapter.
