For some golfers, hitting long irons well is difficult if not impossible. Hybrid clubs are designed to replace the long irons. They look like smaller fairway woods. Like fairway woods they have a much lower center of gravity than long irons heads. That characteristic lowers the center of gravity of the clubhead to be lower than the center of gravity of the ball. The physics of that relationship makes the ball take off and fly higher than it would with a long iron. It makes hybrids much easier to hit.
Some hybrids are very narrow from the face to the back of the head. These will not hit the ball as high as hybrids that are wider from the face back – more like a fairway wood head.
Hybrids are typically 1/2 inch longer for the equivalent iron. For example, the standard length for a 3 iron is 39 inches. The standard length for a hybrid that replaces a 3 iron is 39-1/2 inches. Shafts used in hybrids are either designed especially for hybrid clubs or are the same iron shaft that match the rest of your irons. A hybrid shaft in your set of clubs may be a different brand shaft, but will have similar weight, flex and bend point as your iron shafts. They will play the same other than the head making the shot easier to hit.
Always try out a hybrid you are interested in by hitting it into a net or at a driving range. Because of the wide range of head shapes and weight distribution in the heads, playing characteristics can vary a lot. Don’t get stuck with a long iron replacement that is no better than the long iron you removed from your bag. Check with your local shop, or, if you are near Silicon Valley, contact me.