0 degrees longitude is called the Prime Meridian. It runs from the North pole to the South pole, passing through Greenwich Observatory in England. Greenwich was chosen by international agreement (largely due to it being the de facto standard anyway), though historically other conventions have been used.
The zero reference of longitude is the Prime Meridian.
the Prime Meridian
longitude.
0 degrees longitude
The prime meridian is a line at 0 degrees longitude.
The Equator is 0 degrees latitude, and the Prime (or Grenwich) Meridian is 0 degrees longitude.
longitude
Africa is at 20 degrees north latitude and 0 degrees longitude
The prime Meridian is 0 degrees longitude.
0 degrees longitude
The prime meridian is a line at 0 degrees longitude.
latitude 0 degrees.
the direction that longitude run is 0 the 180 degrees and also east and west
0 degrees latitude and 0 degrees longitude.