The term blit is shorthand for "bit block transfer," which is the process of transferring blocks of data from one place in memory to another. Graphics programmers use blitting to transfer graphics from one place in memory to another. Blits are often used to perform sprite animation, which is discussed later. For more information see, Sprite Concepts.
You can use the IDirectDrawSurface3::Blt and IDirectDrawSurface3::BltFast methods to perform blitting.