In general, the equator is hot because the sun shines directly on the equator as the Earth moves around the sun. The more "direct" the sunlight, the "stronger" the sunlight. "Stronger" sunlight feels warmer. Because the Earth is round, any place far away from the equator is tilted away from the direct sunlight. Places that are tilted away from the sunlight will be colder because the sunshine will be "weaker".

This is similar to why it feels hottest during the middle of the day when the sun is directly above us. When the sun is setting, the sunlight doesn't feel as warm. The sunlight is not as strong during a sunset because it is not as direct. Likewise, the sun shines directly above the equator (making it hot), and other places in the world are cooler because the sunlight is not as direct (not as "strong").