What is it? India has successfully groundtested an indigenously developed upperstage cryogenic engine for use on the next GSLV rocket mission in 2008.
But, what is it? A cryogenic engine works by burning hydrogen in liquid oxygen, which is kept at super-cooled temperatures, hence, the term cryogenic. After the Pokhran Tests of 1998, India could not import the requisite technologies forcing it to develop it indigenously.
What is the advantage? Cryogenic engines are lighter and develop more thrust than standard rocket engines. While they are not suitable for the heavy-lifting job of the first stage, they are perfect for work in the upper atmosphere.
So what? By developing this engine, India can give the GSLV rocket a higher payload and more reliability as well as validating technology, and this will propel India forward in the race to put a man in orbit next decade.