Clojure is a functional Lisp with immutable, persistent data structures. This simplifies concurrency programming, which is becoming increasingly important in a multi-core world.

For the "Why?" of Clojure, see Rich Hickey's talk, "Simple Made Easy" (http://www.infoq.com/presentations/Simple-Made-Easy).

As for the downvotes, content-free comments are typically downvoted. Also realize this site is written in a Lisp (http://arclanguage.org) created by Paul Graham (http://paulgraham.com/arc.html).