A sales pitch is a short presentation given to spark the interest of a potential investor, customer, business partner etc. A good pitch is built to persuade and impress and it is crafted carefully for its audience. The pitch presents the problem and the need behind the product, showing that there is a demand and a potential user group. It then shows an innovative solution to this need. It is also vital to show how the product, for example an applied game, would fit in the existing market and compete there (Unique selling point/proposition). Finally the pitch shows how the solution will be executed and what is asked from the audience of the pitch. For example an investor pitch would describe what kind of funding the company is looking for and how this funding would be used to create a product or service to give maximum return of investment (ROI) to the investor.
Introduction to the four basic elements of pitching your idea: Need, Approach, Benefit and Competition.
Gamasutra (http://www.gamasutra.com/) is a vast resource of game development and gaming business related articles. There you can find a lot of good advice for pitching, including the featured article.