As a child, you may have learned to write a bike with sneakers on, sandals for the summer or even barefoot, but that was before you knew about the benefits of dedicated bike shoes. As an adult, you can still wear sneakers or other footwear for a quick ride around town, but bike shoes provide something extra that street choose cannot give you.
Bike shoes differ from regular athletic shoes in two main ways. First, their souls are stiffer and harder so when you push down on the pedal, more of your energy and force is applied and it takes less effort overall to get going and keep moving. Second, most have toe construction that are specifically made to fit well in clipless pedals. There are also non-clipless petals in which the shoe is actually affixed to the pedal so they cannot slip out during the race for a ride.
Despite their stiffer souls and unique toe box, bike shoes are quite lightweight and are well ventilated for maximum foot comfort. There are types made for road biking, mountain biking and ones that are very similar to street shoes to make it easier to take a bike ride and then walk around the shops or park for a while before riding home again.
In general, street and mountain bike shoes are not ideal for walking because they do not flex and bend like your foot naturally does. Out of the two types, mountain bike shoes are better because they have more rugged and gripping soles so the writer does not slip on rocks or an uneven trail.