§1. By virtue of office, the vicar general has the executive power over the whole diocese which belongs to the diocesan bishop by law, namely, the power to place all administrative acts except those, however, which the bishop has reserved to himself or which require a special mandate of the bishop by law.
§2. By the law itself an episcopal vicar has the same power mentioned in §1 but only over the specific part of the territory or the type of affairs or the faithful of a specific rite or group for which he was appointed, except those cases which the bishop has reserved to himself or to a vicar general or which require a special mandate of the bishop by law.
§3. Within the limit of their competence, the habitual faculties granted by the Apostolic See to the bishop and the execution of rescripts also pertain to a vicar general and an episcopal vicar, unless it has been expressly provided otherwise or the personal qualifications of the diocesan bishop were chosen.
Source: Code of Canon Law (Vatican.va)