The track is for a Jiffy reefing system. It allows you to move the outhaul for the aft reef point depending on where/ which reef you are using (1st or 2nd). You want your outhaul to be down and aft to maintain good sail shape. It also allows for different sails with different dimensions to be used without having to bolt a new point onto the boom.
If your sails aren't to large you can do a single line reefing system as shown here.