Flash basics overview :

Flash movies are graphics and animation for Web sites. They consist primarily of vector graphics, but they can also contain imported bitmap graphics and sounds. Flash movies can incorporate interactivity to permit input from viewers, and you can create nonlinear movies that can interact with other Web applications. Web designers use Flash to create navigation controls, animated logos, long-form animations with synchronized sound, and even complete, sensory-rich Web sites. Flash movies are compact, vector graphics, so they download rapidly and scale to the viewer's screen size.