The playhead is a red vertical line that indicates the current position of playback.
Pressing P will set the playhead to the current position of the mouse pointer, if it is within the editor track area.
A Left click anywhere on the Ruler will move the playhead to that position.
Clicking on either the primary or secondary transport clock and editing their value moves the playhead to a specific position.
Right clicking on the marker and selecting either Locate to Here or Play from Here will place the playhead at the marker's position.
Alternatively, placing the mouse pointer on the marker and pressing P sets the playhead precisely on the marker location.
When the loop transport button is pressed, the playhead will jump the start of the loop range, and continue to the end of that range before returning to the start and repeating.
While looping, a light green area is displayed in the Ruler over the tracks to show the loop range.
By default, looping is bound to the l key.