The track slider is on top of the control buttons. It shows the progress of playing of the media file. You can drag the track slider left to rewind or right to forward the track being played.
Two timers at the left and right ends of the track slider show the current playing position (left) and the total time (right) of the current track.
Note: When a media file is streamed (live), the position indicator of the track slider does not move because the total duration of the streaming is not known until it finishes.