Some cameras offer buffered shooting in which the camera is continually sampling into a high-speed buffer a series of frames and the shutter release just commits to memory. Other cameras offer this as a continuous shoot mode where a single press will start the buffering and a release of the button will then commit the frames. The first method pretty much eliminates shutter lag at the expense of battery time. the second method will eliminate shutter lag if you anticipate the shot and can start the buffer-capture before it happens.