what-is-215-55r17

what is 215 55r17 what size is 215 55r17 215/55r17 to 225/55r17 can i use 215/55r17 instead of 225/55r17 difference between 205 50r17 and 215/55r17 215/55r17 meaning difference between 225/50r17 and 215/55r17