Longitude lines, also known as meridians, are imaginary vertical lines that run from the North Pole to the South Pole. They help us measure how far east or west a location is from the prime meridian, which is set at 0 degrees longitude. Each line is spaced evenly, with a total of 360 degrees of longitude around the Earth. These lines are essential for navigation and mapping, allowing us to pinpoint exact locations on the globe. For example, the International Date Line is located at approximately 180 degrees longitude and plays a crucial role in determining time zones around the world.