Here's a breakdown:

* Prime Meridian: This is an imaginary line that runs from the North Pole to the South Pole, passing through Greenwich, England. It is designated as 0 degrees longitude.

* Degrees East/West: Lines of longitude run vertically around the Earth, forming circles. Each circle is divided into 360 degrees. Locations east of the prime meridian are designated with positive degrees (e.g., 10° East), while locations west of the prime meridian are designated with negative degrees (e.g., 10° West).

* Distance: The distance between each degree of longitude is not constant. It changes depending on the latitude. At the equator, where the circumference of the Earth is the greatest, each degree of longitude is roughly 69 miles (111 kilometers). However, as you move towards the poles, the distance between degrees of longitude decreases, eventually reaching zero at the poles.

Therefore, longitudes mark distances in degrees along the Earth's surface, with the prime meridian as the reference point. The actual distance represented by a degree of longitude varies depending on the latitude.