[ThreeQuarter]

P is for metric passenger car tire (measured in mm instead of inches). Usually these are load range B. LT is for light truck, and can come in higher load ratings. (P-metrics are OK to use on trucks.)

275mm is the section width, includes the sidewalls and whatever amount of curvature they have. Basically the measurement of the tire at it widest point, not including tire squat from a load.

Section height is 60% of 275mm. So the actual measurement depends on width--all 60 series are not the same height.

R is for radial.

15 inch rim diameter.