From Wikipedia:

An elevator pitch (or elevator speech) is a brief overview of an idea for a product, service, or project. The pitch is so called because it can be delivered in the time span of an elevator ride. The term is typically used in the context of an entrepreneur pitching an idea to a venture capitalist to receive funding. Venture capitalists often judge the quality of an idea and team on the basis of the quality of its elevator pitch, and will ask entrepreneurs for the elevator pitch so to quickly weed out bad ideas. It is said that that many of the most important decisions made on the floor of the United States’s House or Senate are made “in the spate of an elevator ride” as a staff aide whispers into a congressman or senator’s ear while they head down to the floor to cast their vote. A variety of other people, including intrapreneurs, project managers, salespeople, and job seekers, commonly use elevator pitches to get their point across quickly.

• A short video explaining the Elevator Pitch.
• A collection of articles from the Kauffman Foundation, “Pitching Angel Investors”.
• Examples of elevator pitches and more can be found at Your Elevator Pitch.