A physical address is the actual number and street name assigned to where you live, including the municipality. For example, "67 Lehigh Street, Fairview Twp" is a physical address. It is stating the number, the street name and the municipality of where the person is located. When calling 9-1-1, you should always use the physical address for the location you are calling from.
A mailing address is the number and street name assigned where you live, but includes the post office from where you receive your mail from and a zip code (which may include a Post Office Box). For example, 67 Lehigh Street, Mountain Top, PA 18707 is a mailing address. When calling 9-1-1, you should not refer to "Mountain Top, PA" as where you are located, because the term "Mountain Top" is the name used by the post office, and does not narrow down which Police, Fire or EMS department responds. For reference, there are 5 different police departments that make up the "Mountain Top" area, along with 5 Fire departments. This is why it is imperative to utilize your physical address when calling 9-1-1.