Demand for quants

From the pioneering work on modern financial economics by Harry Markowitz, William Sharpe and Merton Miller to the revolutionary Black-Scholes formula by Robert Merton, Fischer Black and Myron Scholes, coupled with the advent of rapid technological progress over the past decades, the financial industry has undergone vast changes in terms of complexity and innovation. There is now an ever increasing need for highly quantitative and numerate people - mathematicians, physicists and engineers to work at the forefront of financial markets.

For starters, refer to the following resources for a better definition and introduction to the role of a quant.

wikipedia
Mark Joshi (pdf)