There are many different kinds of bikes. They come in a variety of of sizes, and frame dimensions. It depeneds on what kind of biking you are into.
This is an example of a dirt jumping bike. Many people use dirt jumping bikes like these for riding street too. Although it is not specifically for street, modern drit bikes are made to take all kinds of abuse plus they are usually ligter.
This is an example of a Vert or Park kind of bike. It has 4 pegs and front and rear brakes. This bike also has a for piece bar making it easier to use for park or vert. These bikes are ussually heavier than a dirt or a street bike.
This is a flatland bike. It is similar to a park or vert bike. The frame is different and has different types of pegs. These kind are used to stand on not for grinding. Sometimes These bikes are smaller and have smaller drive train.
This is a racing bike. I don't really like racing. All I know about racing is the bike is light and everything is smaller and skinnier.
