Poaching is when someone hunts or fishes even though they are not allowed to. Wild animals often belong to someone, namely the person who owns the forest or the area where the animals live. The state can also be the owner of these animals. Anyone who hunts these animals without permission is liable to prosecution, just like other thieves.
Even in the Middle Ages, people argued about who was allowed to hunt. For a long time, the nobility had a privilege to hunt. Foresters and master hunters were employed to look after the game. Other people, however, were severely punished for hunting.
Even today, people are not allowed to hunt just like that. Apart from who owns the game, you have to observe the closed season, for example. During this time, hunting is not allowed at all.