The equator is hotter than other areas of the earth, such as the poles, because it receives more direct sunlight than other areas. It is a common misconception that the equator is hotter due to it being closer to the sun than other areas of the earth. However, the earth's distance from the sun is so great that there really is no noticeable difference in distance from the sun.
Since the earth is a sphere, the light rays from the sun do not hit all areas of the earth at the same angle and intensity. Sun rays that hit the poles do so at an angle, covering a larger area with a fixed amount of light. That same amount of light hits the equator, but more directly, and not at an angle. Therefore, the light hitting the equator does so in a more concentrated manner. Other factors can affect temperatures as well, but not as greatly as the angle of sunlight. These alternative factors include differences in atmosphere between the equator and the poles, and reflection off areas that are often covered in snow. Regarding atmospheric differences, when sunlight hits the earth's atmosphere, some of the rays are scattered or absorbed by air molecules. Regarding reflection, snow can cause about 75 to 95 percent of sunlight to be reflected back away from the earth.