The archbishop holds jurisdiction over a province of dioceses, and the essential point about the office is that it is a rank of authority and not a higher grade of ordination.
Jurisdiction, not a new consecration
An archbishop is a bishop who presides over an ecclesiastical province, exercising a limited oversight of the other bishops within it and of his own diocese, but there is no separate consecration for the office: an archbishop is consecrated a bishop like any other and then appointed to the greater jurisdiction, so the fullness of holy orders is already his as a bishop. This distinction, between the sacramental order of bishop and the offices of authority built upon it, runs through the structure of the episcopal churches and explains why archbishop, metropolitan and patriarch are ranks rather than orders.
Where the office is found
The title is used in the Catholic, Orthodox, Anglican and some Lutheran churches, its powers varying from real jurisdiction over a province to a largely honorary primacy, and the greatest archbishops, such as those of the historic sees, carry a weight far beyond their own dioceses. The office corresponds closely to the metropolitan of the Eastern churches, both denoting the senior bishop of a province. Its powers are those of coordination and limited supervision rather than direct rule over the internal affairs of another bishop diocese, which remain the affair of that bishop.