§1. A coadjutor bishop and an auxiliary bishop have the obligations and rights which are determined in the prescripts of the following canons and are defined in the letter of their appointment.
§2. A coadjutor bishop and the auxiliary bishop mentioned in can. 403, §2 assist the diocesan bishop in the entire governance of the diocese and take his place if he is absent or impeded.
Source: Code of Canon Law (Vatican.va)