Normally, a track plays until it reaches the end of the audio file, and then stops by itself. Sometimes you may want the audio file to loop continuously instead. Press the loop button (it has a circular blue arrow on it), and if the audio isn't still playing, press play again. The audio file repeats continuously now.
Try the pan and pitch sliders. The pan control works as you would expect, unless you happen to have your speakers reversed. For the pitch control, far left shifts the pitch an octave down, far right shifts it an octave up, and the middle is "natural" (no shift). To quickly return a pan or pitch slider to the exact middle, Shift+left-click anywhere within the slider.
Left-click within the position slider. Notice that the audio plays from wherever you clicked. This feature is useful for "cueing" (skipping around in the audio).