Due to the shape and tilt of the earth, the equator is always slightly closer to the sun that the areas far from the equator. With the Earth's main source of heat (above mentioned sun) closest to the equator, the equator gets more heating than any other areas, and thus there is a warmer climate.
Another example is if you are in a room with several other people and there is a fireplace, those who are closest to the fire will be the warmest.
