A 195/50 R15 tyre is pretty average and the default tyre size for many cars. Such tyres are produced by all tyre manufacturers, including Kumho, Bridgestone and Pirelli . At the first number you can see, that this tyre is 195 mm wide - at least in theory. In reality it is in fact possible, that such a tyre is only 193 mm wide. When producing the tyre production-related deviations are allowed. This is precisely why the first value of a tyre identification is continued in increments of 10.
While the tyre width can be read off in millimeters, the declaration of the height is not an absolute number. The second number describes the tyre tread as the percental ratio between tyre height and width. With a 195/50 R15 tyre the tread is 50 percent. 50 percent of 195 mm are 97.5 mm, so the tyre height has been calculated. The last number is part of the inner diameter of the tyre. This will be shown in inches and is important, because it is also the rim size that fits for this tyre.