Latitude of a region decides how much sunlight that place will gain, which affects temperature ultimately affecting the climate.
As you can see in the image above (source : https://goo.gl/images/MesL4z) that as we move in northern region from Equator (latitude at 0°) the temperature decreases and when we reach the northern most region, we'll find that it's too cold there.
This happens in the same way as you move down the Equator in sother direction towards south pole.
The main reason here is that Earth is sphere, it has a bulging out surface at 0° latitude and as a result it gains the sunlight the most on this planet and as those rays carry energy and heat the temperature at Equator is conparatively higher than other parts.
As you move up or down the amount of sunlight gained decreases thereofore the climate is comparatively cooler.
These Latitudes also control rainfall as the temperature due to sunlight causes a regular shift in ITCZ (Inter tropical convergence zone) creating pressure differences and hence attracting monsoons.
