Can you explain what targets mean in the init system systemd?

In systemd, targets are special units that serve to group and manage a set of services and other units. They are similar to runlevels in older init systems.

Targets allow you to define which services should be started for a particular system state. For example:

• multi-user.target — corresponds to multi-user mode without a graphical interface.
• graphical.target — multi-user mode with a graphical interface.
• default.target — the default target that is launched by default.
• shutdown.target — the target for shutting down the system.

When systemd loads, it activates a specific target, which in turn starts all related services and units. This allows flexible management of system states and dependencies between services.