Basically air from either north or south of the equator travels to the equator and then heats up, expands and rises. On its trip to the equator it picks up moisture. This moisture as it rises over the equatorial area condenses into clouds and then precipitates creating rain. read more
Also near the equator the sun concentrates its light on a very small area making it very hot. Higher up on the earth ( near the north pole) it is colder as the sun shines the same amount of light over a much larger area. read more