Latitude lines are the horizontal lines on a map.Latitude lines are  parallel to each other they have an equal distant from each other. In the north hamisphere, the degrees of latitude ranges from 0° to 90° N and  in the sorth hamisphere, the degrees of latitude ranges from 0° to 90° S. 0° line refers to the equator, which is the  line which divides our planet into the northern and southern hemispheres. 90° N is the North Pole and 90° S is the South Pole.
     Longitude (meridians) are the vertical lines on a map. They all converge at the two poles (North Pole and Suth Pole), and 0° longitude is located at Greenwich, England (0°). In the east hemisphere, the longitude ranges from 0° to 180°E, and in the west hemisphere,the longitude ranges from 0° to 180°W. Actually the 180°E and 180°W are the same line (so most of the time we just call it longitude 180°). The International Date Line in the Pacific Ocean is defined based on longitude line 180°,but there is a zipzag border on the International Date Line near Bering Sea because that is to keep Russia's north & west territory of the Bering Sea and the United States's  east and south territory of the Bering Sea (which is Alaska), on opposite sides of the line in agreement with the date in the rest of those countries.
     In order to locate spots on the earth's surface, we combine the use of latitude and logitude. Because of accuracy, we not only use degrees (°) but also minutes ('), and even seconds (''). E,W,N,S has to be used to indicate which hemisphere we are refering to. 

Look at the map below: