It allows the programmer to quickly and easily spawn new processes which can talk to each other, but which do not affect each other. For example, if I am a company that wants to support multiple phone calls, and a person is on a phone call, someone else who calls them will get a response saying either "x is busy" or "x is busy, would you like to leave a message?". If this second call terminates, or "crashes" for some reason, it will not affect the first call. The Erlang Movie covers this in more detail.
As a lot of chat-based and interactive web applications surface on the net, fault tolerance is a huge deal, and erlang is providing a good fix. We may see a lot more emphasis on erlang in the near future.
442.   What is erlang (and why should I care?)
  [aestetix/2008-06-01]
441.   What is Conware?
  [jake/2006-12-22]
437.   How do I wash a feather comforter?
  [n0b0dy/2006-08-13]
417.   What is the slashdot amnesia phenomenon?
  [jake/2004-10-29]
398.   How can I fix dhclient in debian stable with the 2.6 kernel?
  [leif/2003-12-20]
384.   Where can I find good undergraduate summer research/internships?
  [virgil/2003-10-03]
381.   What is that pesky System.map file anyway?
  [jake/2003-09-25]
377.   What is a great critical Libertarianism write up?
  [jake/2003-09-22]
344.   Why are you upset?
  [jake/2003-01-29]
341.   Can you give me some pointers for using gpg/pgp and other encryption?
  [jake/2002-12-19]
303.   Is Red Bull really made from bull testicles?
  [strick/2002-02-03]
302.   How can I raise my website's placement on google?
  [macki/2002-01-20]
296.   how do i make a tofurkey?
  [jesse/2001-12-10]
294.   how do i find out what subdomains are in a dns zone?
  [jesse/2001-12-06]
271.   I am stupid and forgot my root password for my OpenBSD box. Now what?!?!
  [ross/2001-09-05]
232.   Where can i find a stamp sized ethernet web server for (barely)less than $100?
  [sidd/2001-05-30]
207.   how can i access a virtual console greater than 12 in linux?
  [jesse/2001-04-03]
202.   Where's a good place to get custom and hard to find computer cables in the Bay Area?
  [rupe/2001-03-19]
187.   So when's the BIG PARTY?
  [strick/2002-01-23]
( nana/2001-03-22 nana/2001-03-21 macki/2001-03-04 )
184.   Just how many people are their, anyway?
  [les/2001-02-22]
96.   Where can I find information on in-vehicle computer systems?
  [rupe/2000-05-24]
88.   Where can I see the adventures of Pumpkin at 2600?
  [josh/2001-04-04]
69.   What is the origin of The Yak?
  [strick/2000-02-28]
20.   What is a good tool to beautify HTML? Can it handle the mess generated by many web-page generation programs, especially the bloated files created by Word2000?
  [jamison/2000-02-10]