THE EARTH is a globe, a sphere. Remember that globes and maps have grids on them called latitude and longitude. With a little practice you can use the grid system to locate specific places on the map. Every place on Earth has an address in terms of its latitude and longitude. For example, the "address" of Ames is approximately 42 degrees North latitude and 93 degrees West longitude. No other place on Earth has this address.
When you look up at the sky it appears to be a dome or a hemisphere (half of a sphere) over your head. But from any single location on Earth, you can only see half of the sky. So the sky is actually an "imaginary sphere" that surrounds the Earth. Astronomers call it the CELESTIAL SPHERE or "sky" sphere. The moon, stars, planets, galaxies, and everything else in the universe seem to be "attached" to the celestial sphere. Ancient observers thought this was true, but, of course, we know it is not. Like places on Earth, each object in the sky also has an address. There are two ways that stargazers can give objects on the celestial sphere an address. They are the ALTITUDE/AZIMUTH system and the RIGHT ASCENSION/DECLINATION system. You can learn more about them at the following links:
Celestial Coordinate Systems.
Lecture 2: Sunrise and Sunset: Apparent Solar Motion