Alright sounds good but what does 245 45 R18 for tires mean?
245 means the tire is 245 millimeters wide. 45 means that the sidewalls are 45% of the width of the tire, the higher the second number the further the top of the tire is from the rim (think truck tires vs low-profiles). The last number is simply what diameter rim the tire fits, and that it is radial construction which all tires are now.
Now, you can fit different width tires on a rim that is say, 7 inches wide and 17 in diameter. You can fit tires 215/225/235 wide for example, but it must be an R17.
Anyways, people use wider tires because they have more contact area with the ground which results in more grip. The same effect can be achieved by lowering the pressure in a narrower tire (fine for drag racing) but will come with some potentially undesired effects. Performance (summer) tires use softer rubber which greatly aids in grip but they come at the expense of longevity. Softer tires will wear out faster and the softest should be reserved only for when you're at the track.