Lines of longitude are imaginary vertical lines that run from the North Pole to the South Pole. They help us measure distances east and west of the Prime Meridian, which is located at 0 degrees longitude. Each line of longitude is spaced equally apart, with a total of 360 lines that circle the Earth. Longitude is measured in degrees, with values ranging from 0 to 180 degrees east and west of the Prime Meridian. These lines are essential for navigation and mapping, allowing us to pinpoint exact locations on the Earth's surface.