Playhead and playmarker
Enter starts playback from the playhead, the position that moves while the project plays. Space starts from the playmarker.
The transport keeps two positions. The playhead is the current one. It moves along the timeline while the project plays. The playmarker is a second start position.
Press Return or Enter to play from the playhead. Press Space to play from the playmarker. Both keys also stop playback. The difference is where they start. The keys are listed with the rest of the transport in Basics.
Follow Playhead scrolls the timeline so the moving line stays on screen. Turn it off when you need the view to stay on a region while the project plays somewhere else.
The loop range, set on the ruler, is the span that repeats. It is separate from both positions.