Hemispheres
The prime meridian and the International Date Line create a circle that divides the Earth into the eastern and western hemispheres. This is similar to the way the Equator serves as the 0 latitude line and divides the Earth into the northern and southern hemispheres.
The eastern hemisphere is east of the prime meridian and west of the International Date Line. Most of Earths landmasses, including all of Asia and Australia, and most of Africa, are part of the eastern hemisphere.
The western hemisphere is west of the prime meridian and east of the International Date Line. The Americas, the western part of the British Isles (including Ireland and Wales), and the northwestern part of Africa are landmasses in the western hemisphere.