205 - This is the section width of the tyre. That means the overall width of the tyre in mm.
55 - This is the aspect ratio of the tyre. That is the sidewall height of the tyre as a percentage of the section width.
R - This means the tyre is of Radial construction.
16 - This is the Rim diameter in inches, e.g. 16" wheel.
91 - This is the load index, which is a code associated with the maximum load a tyre can carry.
V - This is the speed symbol, which relates to the maximum speed of use.