A size often found on compact cars, 195/55 R16 tyres are generally practical models focused on efficiency and comfort. The number 195 indicates the approximate width of the tyre's cross section, expressed in millimetres. The measurement is taken between the two most distant points on opposing sidewalls, and is not the same as tread width.
Following this we have the number 55, representing the aspect ratio. This relates to cross-section height (sidewall height from the tread line to the rim). An aspect ratio of 55 tells us that cross-section height is equal to 55% of width (here, of 195 mm). Do keep in mind that these are standardised, approximate indications.
The final part of the inscription consists of a letter and a number. Here, the letter R' stands for radial tyre' - a common constructive type for light vehicles. The number 16 refers to inner diameter, expressed in inches; you can only fit this tyre onto a 16 inch rim.