/usr/lib/systemd/system/graphical.target:

[Unit]
Description=Graphical Interface
Documentation=man:systemd.special(7)
Requires=multi-user.target
Wants=display-manager.service
Conflicts=rescue.service rescue.target
After=multi-user.target rescue.service rescue.target display-manager.service
AllowIsolate=yes

display-manager.service

/etc/systemd/system/display-manager.service
->
/usr/lib/systemd/system/lxdm.service