A dead pixel is defined as a pixel or set of sub-pixels that has failed and is permanently in the off position. This condition means that the pixel will not let any light through. This can be observed as a dark or black spot on a brightly colored or white background.
A stuck pixel is defined as a pixel or sub-pixel that has failed and is permanently in the on position. This can be either with a single or multiple sub-pixels for a given pixel and is best observed on a dark or black background. A white pixel means all three sub-pixels have failed while a green, red or blue pixel means one of the sub-pixels has failed.