>It's C#'s version of the lazy collection operations you find in most functional languages, just given friendlier sqlish names. (IE, "Select" instead of "map" and "Where" instead of "filter")

Actually........

It's more generic than that. It's C#'s monadic comprehension syntax ala Scala's for and Haskell's Do.

It works on more than just IEnumerable, it actually works on anything that implements Select, SelectMany, and Where...