newbie question: SS

Single speed = Bicycle with only 1 gear with a freewheel on the rear hub; like a "normal" multi-geared bike, the bike keeps rolling if you stop pedalling. You usually need brakes on the front and back to stop the bike, but no shifters.

Fixed gear = 1 gear, no freewheel. Simplistically, if you stop pedalling the bike stops moving; the pedals (cranks really) rotate as long as the wheels are moving. Generally for street use, people might put a brake on the front wheel to aid stopping, but in reality, the bike is mostly stopped using a variety of methods related to stopping or slowing the pedal rotation (and therefore the rear wheel). Skidding or just resisting pedal motion will slow/stop the bike.

Fixed or SS bikes can either road or mountain style frames or a hybrid.

Track bike = bicycle made for racing on the track. Looks like a road bike almost, and has a single fixed gear, no shifters, and no brakes allowed.

No coasting on a fixed gear bike - the pedals move if the wheels are moving. A single speed does allow "coasting", which is helpful on descents and in turns, and sometimes ascents.

A "track bike" has track ends instead of dropouts. Track ends go straight out and allow you to adjust the chain tightness. Technically a track bike is not drilled for a front brake. A bike meant to be ridden on the track wouldn't need to be drilled for a front brakes because they aren't allowed on the track. However, with the increasing popularity of riding track bikes on city streets (see oldskooltrack.com) "track bikes" with track ends are being produced that have been drilled for a front brake. Riding a track bike with a brake is not "old skool" but plenty or people do it. The geometry of a real track bike is also different.

Thanks guys