Before you began to ride a mountain bike you probably would not have given the real tires that you use much thought. A tire is a tire you may have cried, but now that you're getting into your mountain biking you're starting to see it otherwise.
Mountain bike tires are wider and knobber than their street or hybrid equivalents. They offer more grip, additional shock dampening, and a wider surface area.
As you will be depending on your tires for grip, it is necessary to think carefully when buying your next pair. There are many companies from where you can buy “singlespeed wheels”(also known as "singlespeed Reifen" in the German language) at the best price.
If you are planning on doing plenty of sand trails, loose gravel trails, or even riding your mountain bike in the snow then for you it's all about grip. You should try to find a wide tire that delivers a good deal of tread, you could even look for the winter tires which have studs in for added grip.
If you're planning on riding technical paths or simply around town then for you a slick tire is the ideal option. Do not worry though unlike a street bicycle slick, mountain bike slick tires still have tread however they are generally around 26 inches as appose to 29 inches of winter or trail tires.