Bicycle gears are most generally recognized as the gears aside the wheels on a bicycle. More technically, they are the part of the drivetrain (the mechanism that transmits power) that determines the relationship between the rate that you pedal and the rate that the wheel turns. That specific relationship is called a cadence.
Bicycles come with in a varied number of gears. Shifts are the options on handlebars that help select which gear you want to be in. There are also fixed-gear bikes, or single-speed bikes, that only have one gear.
Gears are used so that a cyclist can comfortably ride depending on the type of angle they are riding, whether it be flat, uphill or downhill. Gear ratios depend on the number of teeth on the chain to the number on the rear sprocket.
Related: What is a Hybrid Bicycle
Each type of gear changing mechanism has its advantages and disadvantages. Some include:
1. Derailleur or External gearing. This is when the sprockets are visible and typically have 5 to 11 sprockets. The chain guide is controlled by a cable that is attached to the shifters, which are either a single lever, two levers, or a twist grip. Most bikes have both front and rear derailleurs.
2. Crossover gearing. This style has three chainrings which offers a wider range of gears, great for touring and off-road biking.
3. Alpine gearing. This is specifically a low gear that has a greater average jump to the next lowest gear, making it great for climbing.
4. Multi-range gearing. This gear has about three or four chainrings allowing an easier capability to maintain a constant pedal speed. It is usually found on racing bicycles.
5. Hub gearing. This is when the gears are hidden within the wheel hub. It is often found in road bikes, or specifically designed bikes for commuting and city-riding.
The trick to gears is that you always want to be traveling at the same cadence. You shift gears depending on angle, so uphill requires a lower gear, downhill a higher gear, and flat terrain is a medium gear. You should not be pushing too hard on the pedals, that is what gears are there to prevent.