During your adventure across The Galar Region, you will find a number of Berry Trees. These trees can be shaken to obtain the berries growing on them. After each shake, you will be given the option to keep shaking or to simply obtain the berries that have fallen thus far. The more you shake a Berry Tree, the higher the odds of Pokemon appearing and forcing you into battle with it. Berry Tree Pokemon include Skowvet, Cherubi, and Greedant. Whether you run or defeat a Berry Tree Pokemon, they will still make off with some of the berries. This is the first time that Berry Trees have a risk/reward scenario in the World of Pokemon.
We have questions and answers related to this topic which may also help you: