I will describe how non-invertible global symmetries act on operators in a quantum field theory. The various possible actions are called generalized charges. This provides a stepping stone for understanding physical applications of non-invertible symmetries, as will be exemplified in the case of Ising symmetry. One of the surprising findings of this endeavor is that there exist new and unexplored generalized charges already for ordinary invertible global symmetries! These generalized charges are described by higher-representations of the symmetry group, generalizing the ordinary charges described by ordinary representations of the symmetry group.