The names of all three stars refer to the set: the outer two are named after the "belt" of the Arabs' "Central One" (a mysterious female figure), while Alnilam comes from an Arabic word that aptly means "the string of pearls."
The proximity of the three stars in the sky is an illusion. In fact, the stars at either end of the Belt, Alnitak and Mintaka, are the closest together in space, Alnitak being a little over 800 light-years away, and Mintaka 100 light-years farther off. The central star, Alnilam, is much more distant than either of these, lying on the edge of the Orion Molecular Cloud, more than 1,300 light-years from the Sun. Alnilam is also easily the most massive and luminous of the three stars, so that despite its greater distance it still shines more brightly than its two companions.
Like much of its parent constellation, Orion's Belt is a highly nebulous region of the sky. This is especially true in the direction of Alnitak, where numerous nebular structures are found. The most famous of these is the Horsehead Nebula, a dark cloud that blots out the light from the red-pink streak of IC 424. Also occupying this region are the less well-known Flame Nebula (NGC 2024) and the Lump Star (NGC 2023).