Ultimately your tires only touch the ground over a couple square inches at most, but it is a rather important connection. Tires are specialized to work best on their respective type of terrain, so none do a great job in every condition.
When picking a tire, first determine what kind of pressure you want it to have. Most road tires can be run at 110 psi or greater, while some tubeless mountain bike
tires can be run as low as 20 psi.
On hardpacked conditions, the center ridge of your tire is very important. The closer it is to continuous, the less rolling resistance it will have. On softer terrain, having a wider tire with more knobs to propel you forward (almost like the prop on a paddle boat), is the way to go.
There are several different tire formats to consider as well, each with their own specific advantages and disadvantages, such as clinchers, tubulars, and tubeless tires.Full Article