Parallel is an alternate term for a line of latitude on a map, while meridian is an alternate term for a line of longitude. Lines of latitude are located parallel to the Equator and never intersect, which is why they are also called parallels.
The lines of longitude on a map all intersect with each other at the North Pole and South Pole. They run up and down from the two poles around the globe. Coordinates are measured and read in terms of degrees latitude and longitude. Zero degrees for latitude is the Equator, while zero degrees for longitude is the Prime Meridian.