Image slicing is a time saving technique that allows web developers to mockup a design in a graphics program, and then have the image be "sliced" along guides. The result is often HTML table along with the several sliced images that appear as the larger image when shown together.

The real time savings come with there is the inevitable change, and the image has to be resliced and exported again.

This is one of the features of Photoshop that someone evaluating the Gimp might miss.

Fear not! The feature is easily available, although it may not be installed by default.