That's a difficult question, and one that will lead to different answers. According
to some, the Middle East (or Mideast) is a part of Asia, sitting where that continent
bumps up again Europe. To others, its a larger region that stretches from Turkey to
northern Africa (above the Sahara) and eastward to Iran. For some, it's a geographic
grouping, for others a political one, and for still others a cultural one.
But why "middle"? Well, the Middle East is a Eurocentric concept created by the British
foreign service in the latter part of the 19th century to describe the area west of
the "Far East" (China, Japan...) but east of Western Europe.
Such a new term for a region full of such old cultures! Some of the world's earliest
known civilizations -- the Sumerians, Babylonians, Assyrians -- arose here, and it's
the cradle of the three Abrahamic religions: Judaism, Christianity, and Islam.