Overview Bar and Markers
Overview Bar
The Overview Bar is closely related to the transport. It is a large slider indicating the current transport position. The slider thumb can be moved using the mouse. Doubleclicking anywhere starts the transport from that position, clicking the thumb stops it. The Overview Bar also shows the markers.

The most recent transport start position appears in the upper half as a green triangle. If you click it, the transport moves back to that position. Double clicking it starts the transport at that position.
The part that's currently visible in editors is indicated by a thin line. It's only visible while the editors are scrolling horizontally.
Markers
Markers are used to name certain parts of a song (for instance: Intro, Verse 1, Verse 2, Solo, Verse 3). Navigating through a song becomes significantly easier using markers. The position counter menu features an Add Marker option, which adds a marker at the current transport position. If there's already a marker at that position, a Delete Marker option is presented instead.
Alternatively, markers can be added by right-clicking the Overview Bar. Most editors allow adding markers by right clicking the time grid area at the top.
An easy way to add markers "on the fly" is to press Ctrl+M (Windows) / Option-M (Mac) at the appropriate times while the song is playing. This takes the grid snap setting into account, so accurately adding markers on the fly is easy when using a grid spacing of one bar while the "Snap" button is engaged.
The markers appearing on the Overview Bar can be left clicked to jump to the corresponding transport position. They can be right clicked to delete, rename, quantize to the grid, move to the current transport position, or type a new position. Renaming can also be done by double clicking the marker. Markers can be dragged to a new position.