In alloy wheel sizes eg 165/70 13. What does 70 mean?

ok its measurd in mm. 165 is the width the 70 is the side wall of the tire it is 70 percent of the tires width and the 13 is the rim size that is one little tire like a dognught , a 165/65/13 will fit the same car as long as all for tires are the same the side wall will be a little lower..so all for corners should be the same size..