I'm mostly thinking of those interstitial lead-in thingies on live and concept albums. E.g., if you let a CD play from track 1 to track 2, there may be 5 seconds of crowd noise leading in to track 2. CD players would show this as track 2 at timing "-5", then count down to zero to get to the actual beginning of track 2.
If the user skipped directly to track two, this interstitial thingy wouldn't be played.
Edit: wording
Also: same question for what.cd ripping process. IIRC they broke the tracks down into different files.