It's from the Greek and Roman perspective of the Orient and the Occident. Initially just words to describe which way the sun sets, they eventually became geographical abstractions, "the East", "the West".

Since Europe was the western edge of a world known to continue on and on, seemingly endlessly, to the east, those abstractions were well in place by more modern times, when you could look at it more logically and say "well you can go east and west from any point, so why is this the West?"

Modern history follows the same pattern. The 'Near' East is nearest to Europe. 'Middle' East, etc.

hi! assuming you're asking about the concepts of "the West" and "the East", you'll find some related questions here

• What does "the West" mean? - contains a short comment, and links to a couple of interesting posts

not quite what you're asking about, but it's also worth being aware of a more formal East/West divide: The Great Schism

• Is Ancient Greece considered western and Byzantium eastern?

• What events lead to the East-West Schism and why couldn't Rome and Constantinople reconcile?

• Could you explain why the eastern schism occured and what it lead to?

• At the time of the Great Schism, what were the main differences (doctrinal, aesthetic, architectural, stylistic) the Latin Catholic and Byzantine Orthodox Church ?

• Why did the Great Schism happen, and why did the Eastern and Western churches develop different traditions?

It's just from the different sides of Eurasia. Europe is to the west, Asia is to the east, and in between is the Middle East. The west's colonies became part of "the West."