What is the difference between an "optical zoom" and "digital zoom"?

What is the difference between an "optical zoom" and "digital zoom"?

Tim Smith (Camcorder Training Specialist) gives expert video advice on: What is the difference between an "optical zoom" and "digital zoom"?; Should I ever turn off my camcorder's image stabilizer? and more...

When you're selecting a zoom, you're going to have a choice between either the optical range, or the digital range, and pretty much every camcorder out there has both optical and digital zoom. What you really want to look for is the optical zoom. It has the best picture quality. When you move past the optical range into the digital range, you're now, instead of optically magnifying the chip, doing it electronically. You're blowing it up on the chip itself. It'll make the image look closer, but the more you go into the digital world, the digital zoom world, the poorer the picture quality gets. So really, if you have to, go for a digital zoom, but try to keep it in the optical zoom world for your best picture quality.