The lateen sail, known for its triangular design, revolutionized sailing as a whole. Aside from the mast, it was also fitted to a crossbar (which would later become the sprit or the boom) that would allow it to swing across the boat to better catch the wind. This new shape and rigging allowed boats to not only accommodate more sails at a time, but also allowed the sails to take the wind from the side angles and still move forward. This allows boats to continue sailing even when angled into the winds, and even allowed upwind sailing through the use of tacking and jibing.
Tacking and jibing are the processes of moving the sail from one side of the boat to the other. Tacking involves turning the boat to the starboard side, while jibing involves turning the boat to the port side. Sailors use this to sail in a zigzag pattern when traveling upwind, that way they can effectively travel into the wind without ever actually steering directly into it.
This type of sail and rigging were first used within the Mediterranean, around 2000 BC, and spread through the region rapidly due to their prominence. These sails have been regarded as potentially the most important invention in sailing, since they allowed sailboats to travel anywhere at anytime.