Samplers work by taking a sample, a digital recording of a sound (much like a cd) and stretch it up and down the keyboard so it can be played musically. There are various algorithims (boy, I can't spell-sorry) for doing this some of which are better than others. Often strange artifacts are introduced into the "notes" when they are stretched too far, so complex waveforms like vocals and saxes are "multisampled"...i.e., several samples are taken a given interval apart. Often a sample is looped to conserve memory...e.g., a sound like an organ which essentially repeats is given loop points so the same section of the sample plays as long as the note is held down. Anything can (and probably has been) sampled, some with better results than others.