A track bike is designed especially for adrenaline-pumping, fast-paced racing at a steeply sloped velodrome or outdoor track. It is a fixed-gear bike (one gear only), it does not freewheel (so when the wheel is moving the pedals will keep moving) and it has no brakes (you just pedal slower to stop!).
Track bike tyres are narrow, often tubular, and inflated well to reduce any rolling resistance and allow you to cycle as fast as your legs can go. Their steel, aluminium, carbon fibre or titanium frames are made as rigid as possible and, compared to a regular road bike, have a higher bottom bracket so the pedals don't touch a steeply banked track. It will also have a steeper seat tube to make your position more aerodynamic, a steeper head tube for more responsive steering and less fork rake (straighter forks).
