What is optical image stabilization on a camera? Good or bad to have?

image stabilization will reduce the effect of your shaking hands during low light condition to a certain point. Some people find it to be very useful - but only to a limit. You can take better picture but moving object will still be blurry anyway and too dark a light in a room and your picture would still be blurry. I can live without it, but it would be a good help if I do.