A bicycle, also known as a bike or a pushbike, is a vehicle that has two wheels and is propelled by pedals. Bicycles can be dated back to 19th century Europe, and have evolved gradually into several designs and models available today. Bicycles are an ideal means of transport--non-polluting, quiet, small, easy to maneuver, light and inexpensive. They can be used by anyone, from a 5-year-old to a 70-year-old. Bicycling is also a very good form of exercise. However, there are a few disadvantages of bicycles: they cannot be used for great distances and they also tire out the rider after sometime. This is the reason for the evolution of the engine-powered bicycle or motor bicycle. Bicycles are still being used a chief means of transport in most countries. There are also some jobs where employees depend on bicycles, like postal services, police services or retail delivery.

A bicycle works on the simple mechanism of pushing the wheels forward by driving the pedals in a circular motion. The pedals are connected to the wheels by an iron chain. A steering rod helps to keep the bike balanced. The main parts in a bicycle are the main frame, the drive train, steering rod, the seat/seats, brakes, and optional gears.

Bicycles can be categorized into many kinds based on the function (mountain bikes, racing bikes, messenger bikes, touring bikes, utility bikes, and Randonneu or Audax bikes), number of riders (tandem/twin, triplet bikes and multi bikes), construction (penny farthing, upright, recumbent, folding, moulton, exercise), gearing (internal hub gearing, shaft-driven bicycles, single-speed/fixed gear, retro-direct, and Derailleur gear Bicycles), sport (track, time trial, cyclo-cross, BMX, Triathlon etc), means of propulsion (pedal, rowing, hand-cranked, motorized, shaft-driven, flywheel etc), and several other types, like cruiser bikes, freight bikes, cycle rickshaws, clown bikes, velomobiles/bicycle cars, hybrid bikes, art bikes, unicycle and so on.