The equator is the hottest area bc it's closer to where the sun rotates and the further away you go from it, the colder it gets.
So basically the Suns rotation, the equator runs east and west, and the sun rises in the east and sets in the west so it doesn't get close to the northern and southern parts of the world, so they are colder.
I hope that helps, it's like 4am here lol. I'm tired