Trimarans are an entirely different deal, as they trend more toward the performance end of the spectrum, and can regularly double the sailing speed of monohulls on nearly any point of sail. Keep in mind that catamarans and trimarans are, however, much more sensitive to loading.
A mainsail is a sail located behind the main mast of a sailing vessel. On a square rigged vessel, it is the lowest and largest sail on the main mast. On a fore-and-aft rigged vessel, it is the lowest and largest and often the only sail rigged aft of the main mast, and is controlled along its foot by a spar known as the boom.
A spinnaker is a sail designed specifically for sailing off the wind from a reaching course to a downwind, i.e. with the wind 90°–180° off bow. The spinnaker fills with wind and balloons out in front of the boat when it is deployed, called flying. It is constructed of lightweight fabric, usually nylon, and is often brightly coloured.