the tire rack has a bunch of great info on this topic.
http://www.tirerack.com/tires/tiretech/tiretech.jsp
some info from there, the traction grade for the tire is almost allways A or AA, and is only for straight wet traction. not cornering or dry grip.
the treadwear gread is a percentage. it is based off of a standard 100. i have no idea what the standard is, but a 200 rating should last twice as long as a 100. a 300, 3 times as long. our dunlop sp sport 9000 are a 280.
and for tire sizeing, the numbers on the sidewall are not exact. all 215's are not the same width, not even from the same brand. most companys list the section width and tread width for each tire. but that is not exact either. the section width is measured on a tire that has no load on it. the tread width has no standard for how to measure a tread block that has a curved edge. that is left up to the manufactuer.
and for tire hight, rotations per mile is the usual rating for that. the smaller the number the bigger the tire. but that is also left up to the manufacteur to determine how to do.