Timeline

At the top of the track display area is the timeline display. This consists of a number of rulers, a meter track, a tempo track and the marker display.

Click to enlarge

There are several options to visualise or hide, depending on what you like or need to use for your session.

To open or hide the timelines, just click with Button2 on the left grey area of the timeline and a pop-up window will come out giving you multiple choices:

Same thing can be done from the menu View - Rulers.

Min:Sec

Is an absolute time signal code ruler measured since the start of the session shown as Hours: Minutes: Seconds: Milliseconds

Timecode

Is a time signal code ruler used mainly for syncronization, shown as Hours: Minutes: Seconds: Frames.
The number of frames depends on your menu Option - Timecode fps settings.

Samples

Is a ruler describing the number of samples used in your session, measured from the beginning depending on the sample frequency of your session.

Bars & Beat

Is the musical ruler shown as bars and beats, depending on the meter ruler of the session.