The teeth you see in the photos aren't the same as the things you and I carry around in our gums. Unlike lizards and mammals, somewhere during their evolution birds lost the ability to produce enamel. Enamel is the tough white stuff that coats our teeth and which makes them so hard. So those goose teeth wont be as hard as your own but they would still come in handy cutting through things like grass. They would also let the goose get a better grip on slippery things like snails. What this photo shows is a row of sharp points, or serrations, inside the beak. Scientists have a word to describe those serrated birds teeth. They call them tomia.