Treadwear is expressed by a number that's relative to a baseline wear number of 100. So a tire with a treadwear rating of 200 will wear twice as long as the baseline, a 600 rating would wear six times as long, and so on. As a rule, high-performance and ultra-high-performance tires have lower treadwear numbers than mass-market tires due to their softer tread compounds. A max-performance Bridgestone Potenza S-03 Pole Position has a treadwear rating of 220, while a high-performance Potenza RE950 is rated at 400, and an all-season BT70S carries a 460 treadwear rating.
Traction grades the tire's ability to stop on wet pavement and is expressed by a letter grade, with A being best and C being acceptable.
The temperature grade describes the tire's ability to resist heat generation during laboratory testing. It, too, is expressed by a letter grade, with A being best and C acceptable. The government won't let a company sell a tire in the U.S. that receives less than a C grade.
After that, the data on the sidewall isn't all that interesting. One thing to note, though: The inflation pressure listed on the tire is the maximum inflation pressure, not necessarily the inflation pressure that's recommended for that tire on your car. That info can usually be found on a sticker in the doorjamb, or in your owner's manual. Recommended inflation pressure is, by the way, for the tire when it's cold. So you should always check the air in your tires when they're cold. What's "cold" according to tire manufacturers? Do it first thing in the morning, before you start driving. Or wait three hours after you stop driving. Otherwise heat in the tire will raise the air pressure, and you won't get a true reading.
There are tons of different tread patterns out there, but they generally fall into four different types: directional, nondirectional, symmetrical, and asymmetrical. The first two terms have to do with the pattern as it goes around the tire. A directional tire has a tread pattern that is designed to grip best with the tire rotating in one direction only. These tires are pretty easy to spot; they're the ones with a tread pattern in a V or arrow shape. These have to be oriented a certain way when mounted so that the pattern is pointing in the right direction. Just in case there's any doubt as to which way that is, there are usually arrows printed on the sidewall that point in the direction of proper rotation.
A nondirectional tire has a tread with grip characteristics that work with the tire rotating in either direction. There's no need for special mount orientation for this type of tire.