The first issue that we see  indicates the width of the tire in millimeters. Usually values between 125 and 335.
The second number, preceded by “/” indicates the tire height. However, this value is expressed as a percentage of the width.
The letter that we find immediately after the height, the most common is “R”, therefore represents the type of tire construction. “R” means radial, “ZR” Suitable for high speeds, “RF” indicates Run Flat.