The locations found will not be limited to the specified area code.
Some area codes cover a very large geographic area, up to an entire state.
Searching for a location near the center of a large area code may not find locations near the boundary of that area code. The exchange is the first three digits after the area code. You would enter 123-456 to search for locations nearest this exchange. An exchange usually covers a small geographical area, so it provides a more accurate location than its area code.