Bicycle shoes for road cycling
Assuming that you're talking about cleats on your shoes, there are three main attachment systems.

Left: 2-bolt, Middle: 2 or 3 bolt, Right: 3 bolt.



Notice how the one on the left has a chunkier sole. The two-bolt option is used for SPD which are popular with MTB, commuting and touring cyclists. I use 2-bolt SPD shoes on my audax bike because I'm able to walk in them without slipping over or damaging the cleats.

A comparison of the different pedals has already been covered thoroughly on bicycles.SE, and Wiggle also provide some friendly explanations.