See that number after the capital letter(s)? That stands for the tire's section width, meaning the distance from the inner edge of the sidewall to outer edge in millimeters.
After the tire width, you should see a slash and then another number. That number is known as the aspect ratio. It is the section height compared with the section width. You'll more than likely see an R after the aspect ratio. This means "radial."
The number after the R indicates the rim diameter for which the tire was sized.
Next comes the number indicating load index. This value indicates the amount of weight that the tire was designed to bear. The number itself is not the weight, but a number that correlates to a certain weight. For instance, a common number is 95, which correlates to a weight of 1,521 lbs. But that is per tire, so a set of tires--all rated at a load index of 95--can bear 6,084 lbs.
Following the Load Index is the speed rating, represented by a capital letter. The speed rating tells us the top speed at which the tire can be run and remain safe. The letter H, for example, indicates a speed rating of 130 mph.Often, the only information people are used to getting from a tire's sidewall is the maximum permissible inflation pressure. Remember, this the only the maximum, not the ideal pressure. You can find that in your owner's manual.