No matter what type of off-road cycling you do, you need to buy MTB tires that work best for your bicycle and your ride style. Some people are quite happy to keep the stock MTB tires on and do not shop around for other options. However, this is not always the best idea, especially if you ride an awful lot or want to be competitive.
MTB tires come in both tube and tubeless varieties. Options with the tube are easy to find and less expensive than the other type, but may cause problems with punctures or wear on the trail. MTB tires that are tubeless cost more to replace but they hold up better on rough terrain.
When it comes to speed and performance on the trail, the width of the MTB tires and what shape they are plays a very important role. Some tires are more square-shaped on the bottom which leads to a greater surface area touching the ground. This could be slower but more maneuverable. Other tires are rounder in profile and can be run with less air in them if you want more contact or pump up more for less friction.
The other main factor to consider with MTB tires is the tread. Because you will be riding over loose sand, packed dirt, rocks, fallen branches and other natural terrain, slick street tires will not do. The tread on tires can be very thick and knobby, have shorter knobs, have tread only view the center of the tire or have tread from edge to edge.