There are many different kinds of tires that can go on a car or truck. They range from tread depth measurements in parts of an inch to full inches, being able to handle 90mph all the way to over 200mph, needing 30 psi to 130 psi. They can differ almost as much as the vehicles that they come on.
Car tires come in all sizes, shapes, load ratings, and speed rating. To start with it is important to understand to the load and speed rating (these are the same on car and truck tires). Load rating is measured from 70 to 110, 70 being able to hold the least (761 pounds) and 110 being able to hold the most (2337 pounds). Speed rating is how fast a tire is capable of going safely. The measurement is a little more confusing than load rating, it is measured between L and Z with no X and an H. However the order from greatest speed to least is LMNOPQRSTUHVZWY. W and Y are reserved for the fastest supercars with capabilities well over 150 mph. These rating usually appear next to or within the size. For example a 205/60/16 89S has a load rating of 89 and a speed rating of S.
They also come in many different sizes. Size is in a series of 3 number. The first number is the width of the tire in millimeters. The second number is the height of the side wall in percentage of its width. The third number is the diameter of the wheel the tire is designed to fit on. So a 205/60/16 has a width of 205 millimeters, a height of 123 millimeters (60% of 205), and fits on a 16 inch wheel.
Tires also have ratings to specify what type of vehicle they go on. These ratings are P,T,LT,C, and ST. P stands for P-metric, and these are designed for passenger vehicles such as cars, mini vans and some SUVs. T stands for temporary, and this designation is given to spares. LT stands for light truck, and these are have more ply than P and are designed to go on vehicles that carry cargo. C stands for commercial and these go on semi trucks and cargo vans. Lastly, ST stands for special trailer, and these tires are designed to only be used on transportation trailers.
Car tires also come in many different shapes. The first and most common is symmetrical. Symmetrical tires are the same on both sides and have mirrored tread on the left and right sides. They can be mounted on the wheel either way and they will be the same.
Another kind is an asymmetrical tire these are designed and labeled with an inside and an outside. These tires can only be mounted on a wheel one way and function properly. Asymmetrical tires are designed to push more of the water either underneath or outside of the car, depending on the design. They are the second most common kind of tire.
The third and last kind of tire is directional. These are characterized by the tread looking like an arrow pointing one way. They are most similar in looks to a symmetrical tire and can be mounted on a wheel either way. However depending on which way the tire is put on the wheel it will either be for the left or right side of the vehicle. The biggest disadvantage to directional is that they cannot be rotated properly because they are made for a specific side of the vehicle.
Trucks do have some special types of tires. The first thing to understand about truck tires is ply. Ply is how thick a tire is, this determines its load bearing capabilities and how much air it can hold. Ply comes in 6, 10, and 14. 6 ply is for light truck and quarter ton and usually hold 35psi. 10 ply is for half ton and one ton trucks usually hold between 60 and 80psi. 14 ply is for large trailers and semi trucks and can hold over 100psi.
Truck tires also come in all terrain with are like street tires but with a deep wider spaced tread. This is so they can grip better in soft dirt, grass, sand, and light trails. They come stock on most trucks, jeeps, and some more aggressive SUVs. The disadvantage to this type of tire is less comfort on the road then you would get with a street tire.
The other option for trucks is the infamous mud terrain. These tires are characterized by huge widely spaced tread blocks. They have a very aggressive look, and are designed for much better traction in mud, wading in water, and in sand. The disadvantage to this type of tire is that there is greatly decreased road comfort and an increase in road noise than you would get with a street or all terrain tire.