P - Passenger car tyre. If there is no P before the size it would indicate it is a European metric tyre. An LT before the size would designate a light truck tire.

205 - This is the Section Width in millimeters. This measurement is taken from sidewall to sidewall.

65 - This number refers to the height of the sidewall, or the Aspect Ratio. It is a percentage of the section width. In this example, you would take 65 percent of 205 millimeters and this would give you the sidewall height.

R - Radial tyre construction.

15 - Wheel diameter in inches.