Here's a pretty descriptive photo...
He's holding two different types of wax rings. The one in his right hand is a basic wax ring. Just wax. The one in his left hand is wax surrounding a thin plastic flange that helps direct the poo to the drain hole. Sometimes you need the one with the flange, sometimes not. It will usually work, and is usually the one I go with.
Note the floor flange in the floor. His is white PVC. Yours may be brass or another metal.
Also take note of the two tank bolts sitting vertically in the floor flange. They go through the corresponding holes visible in the base of the tank. Nuts and washers hold the tank down.