The sun is a rotating sphere. It has a diameter of 32 miles and is located approximately 3000 miles above the surface of the earth.
The Sun's area of light is limited to an elliptic area of light upon the earth much like the light of a lighthouse is limited to a finite area around it. The rotating light on a lighthouse does not propagate infinitely into the distance. This means that only certain portions of the Earth are lightened at a time. It also describes how night and day arise on a Flat Earth. The apparent view of rising and setting are caused by perspective, just as a flock of birds overhead will descend into the horizon as they fly into the distance.