Distance measured for longitude and latitude is typically expressed in miles or kilometers, depending on the context. Longitude and latitude themselves are measured in degrees. To specify distance, you'd convert these degrees into miles or kilometers based on the Earth's circumference.
1 degree of latitude is approximately equal to 69 miles (or 111 kilometers) everywhere on Earth. However, the distance represented by a degree of longitude varies depending on the latitude and ranges from about 69 miles (111 kilometers) at the equator to 0 miles (0 kilometers) at the poles.
In summary, the distances related to longitude and latitude are ultimately measured in miles or kilometers.