Drop Handlebars
Drop handlebars on a road bike
Drop handlebars are the kind of bars typically found on road or track bikes. They're distinguished by the "drops," curved bar ends that extend below the level of the bar on both ends. Cyclists can choose from a variety of riding positions when using drop handlebars: They can put their hands down into the drops to lower their body when going fast, put their hands onto the tops of the drops, behind the brake levers when riding at a more relaxed pace, or place their hands near the center of the bar when they want to sit in a more upright position, as when they're climbing a hill. The bars will be wrapped in cork or synthetic "bar tape" which provides the rider a good grip wherever they choose to put their hands.
Flat Bars
Flat bars on a mountain bike
Flat bars are the type of bars found most often on mountain bikes, hybrids and cruisers. There are some variations in shape, but they're distinguished by a basically straight shape and the placement of grips on the end of the bar. Shifters are usually integrated into the grips so the rider can maintain his grip on the bike while shifting gears.
Aerobars
Aero bars on a triathlon bike
Aerobars are a specialized type of handlebars used on time trial and triathlon bikes. When using aerobars, the rider rests his forearms on a set of pads and grips a set of bars which extend straight out in front of the bike. This allows the rider to stay very low on the bike and reduce wind resistance. Steering is accomplished mainly by shifts in weight and position of the forearms, so learning to ride well on aerobars is a somewhat advanced skill. Aerobars also feature a set of handlebars to the sides called "bullhorns," which offer a more conventional riding position when the cyclist is going slow or wants to sit in a more upright posture.
