I'm aware that when moving a piano, especially a good one, care must be taken and using a proper mover is strongly recommended. But what is actually involved in moving a piano (other than lifting the thing up and making sure it can't slide around)? What makes it tricky and what damage can occur if it's not done properly?

As a side question, what counts as "moving" a piano? My neighbours have moved theirs from one wall to another in the past and I'm sure you sometimes see pianos wheeled onto stages so is literally any motion a problem or would sliding it be OK - for instance on a slippery laminate floor?