There are three basic styles of BMX bicycles, Race, Jumping, and Freestyle. They are very similar in design and all work well on the track. We ride BMX because it is fun, and any style BMX bike is great for that!
Race style BMX bikes are designed to be light and strong. Most are made of Cro-moly steel or Aluminum because of the strength to weight ratio of the material. They came in several sizes to best fit the riders body, arm, and leg lengths. The most common sizes are Mini, Junior, Expert, Pro, and ProXL. Each size has components fitted to it that match the riders dimensions. Top tube lengths, wheel & tire widths, crankarm length, gearing, and handlebar size dimensions are examples of the differences between the bikes. The younger riders benefit the most from having a bike designed to their specifications and find it much easier (and often faster) to get around the track.
Jumping style bikes have been very popular in recent years. They have stronger frames to withstand the abuse of big jumps and jumping. They also have heavy duty components fitted like oversize axles and wheel assemblies. They weigh more that a race bike because of the heavy duty nature of the bike. Most are made to Pro sizing specifications.
Freestyle bikes are closer to a Jumping bike than a Race Bike. They are made in the Pro size range and have components fitted to them that make doing tricks easier such as cable rotors and freestyle pegs that attach to the axles. They too are made in the heavy-duty fashion to withstand jumps, tricks, and grinds. They also have front brakes for doing tricks that the Race bikes go without. Remove the freestyle axle pegs before bring the bike to the track.