What's different is not so much the language (though it is likely unlike anything you've ever used before) but the extreme focus on reliability, error handling, OTP, BEAM and all the other Erlang goodies. All of the parts are impressive individually, they work together to create something that is in my opinion unparalleled in the software world. Read this paper to get a much better idea of what makes this a very unique combination of elements: https://erlang.org/download/armstrong_thesis_2003.pdf

Good luck!