These two terms are often used interchangeably, but have a different meaning that I have mumbled about from time to time. This post on the PARC blog in response to Malcolm Gladwells article in the New Yorker is terrific articulation of the difference.

“Simply put: “invention” is the manifestation of an idea or creation of something new. It doesn’t become an “innovation” until it’s applied successfully in practice”

Gladwells article examines the often told story of Steve Jobs visit to PARC where he saw the work being done by PARC scientists on user interface and early mouse, and raced back to the Apple garage, changed the direction of the development programs, and brought the first Macintosh to the market.