Touring bikes are the perfect bike for long distance and traveling with extra gear. These bikes are built for comfort and are light-weight, yet they have sturdier components for durability. Touring bikes typically have lower gears to pedal up steep inclines and stable frames to carry large loads.
Triathlon bikes are a variation of road bikes that are made for speed on the road during your race. These bikes are designed primarily to optimize aerodynamics. Typically in triathlons, cyclists don't draft as in many other forms of road racing - therefore, triathletes can gain a significant advantage by riding a bicycle that can reduce wind resistance. Everything on triathlon bikes, from the frame to the wheels, helps a cyclist ride faster.
Cyclocross is a type of bicycle race that combines various course types into one. Your bike can be on pavement, grass, steep hills, wooded trails and even on your back during the race. Therefore these bikes are relatively light-weight but have durable, wide tires to handle the tough conditions of the terrain.
A fixed gear bike means the bike has a drivetrain with no freewheel mechanism, meaning the riders can't coast. They only have one gear. This type of bike has became popular among urban commuters because they are lightweight, due to the fact they don't need parts required for a fully geared drive train, and because these bikes provide a simple riding structure.