That's the "Prime Meridian".
an imiginary line denoting o degrees longitude
Mexico is west of the Prime Meridian (0° of Longitude).
The Prime Meridian is made up of all the points with zero longitude and every latitude.
longitude.
00
prime merdian
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
The International Date Line (IDL) is a line of longitude located at about 180 degrees east (or west) of the Greenwich Meridian.
The coordinates 20 degrees north and 0 degrees longitude point to Africa. Specifically, it is near the border of Algeria, Mali, and Niger in the Sahara Desert.