The wider your rim - the lower your tire height. Get a better idea on wheel fitment based on the tire and rim combination that you have.
The two-digit number after the slash mark in a tire size is the aspect ratio. For example, in a size P215/65 R15 tire, the 65 means that the height is equal to 65% of the tire's width. The bigger the aspect ratio, the bigger the tire's sidewall will be.