Let's see what each symbol means.

195 mm(Section Width):

·         Nominal section width of the tyre in millimeters.

65(Aspect Ratio):

·         The sidewall height as a percentage of the section width.

·         For example, sidewall height of this tyre will be 195 x 0.65 = 126.75 mm

R(Radial construction):

·         Denotes radial construction which is dominant for passanger tyres.

15(Rim diameter):

·         Rim diameter in inches to which the tyre fits.

91(Load Index):

·         Load capacity of the tyre which is the maximum weight the tyre can carry.

·         You may look-up the value in the load index table.

T(Speed Index or Speed Rating):

·         Maximum speed at full load. You may lookup the value in the tire speed rating table.