The systemd Type= value. Leave as default for ordinary long-running commands unless the service needs another startup protocol such as forking, oneshot, or notify.

simple treats the started process as the service immediately. exec is similar but waits until the command has been executed. forking is for daemons that background themselves and often needs a PID file. oneshot is for short tasks that exit. dbus and notify wait for D-Bus ownership or systemd readiness notification. idle delays execution until other jobs are dispatched.