I am a math teacher and a tutor. I am not a science teacher, but I have traveled around the world quite a bit. I will try and answer your question.
The earth rotates on an axis and is tilted (I think it's 23.5 degrees). This tilt changes what type of season you have. For example, the United States is having Winter right now. Of course, if you're in Naples Florida and are closer to the equator, it is 80 degrees. If you are in Australia (down under), you are having summer. When we have Spring, Australia has Fall. The tilt of the earth makes the seasons opposite.
The closer you are to the equator, the warmer it gets. However, altitude is another factor that can change the temperature. For example, when I was in Africa, right on the equator, it was extremely hot (105 degrees). However, there was snow on Mount Kenya because of the high elevation of the mountain.