A punt is a flat boat with a broad front. It is designed for use in small rivers or other shallow water. Punting means boating in a punt. The punter pushes a pole against the river bed (the bottom of the river) and this gives the punt a way to move.
Punts were originally built as cargo boats or platforms. They were for shooting at birds and fishing. In modern times they are mostly used for pleasure trips on the rivers in the university towns of Oxford and Cambridge in England. There are also races at summer regattas on the Thames.