The Bishop is the first and highest degree of the clergy out of the Orthodox Church (episkopos in Greek, which means overseer). He is the successor to the Apostles out of the service and government of the Church. A bishop will be responsible for and the head of all the parishes located in his diocese. All authority of the lower orders of clergy is derived from the bishop. No divine services may be served out of any Orthodox temple without the authorization of a bishop.
Rankings of Bishops
In the degree of their ordination, all bishops are equal. Nevertheless, there are distinctions of administrative rank among bishops.
Archbishops and Metropolitans
The title of archbishop or metropolitan may be granted to a senior bishop, usually one who is in charge of a large ecclesiastical jurisdiction or archdiocese. He may or may not have suffragan bishops assisting him. In the Slavic and Antiochian traditions, a metropolitan outranks an archbishop. The reverse is true in the Greek tradition.
The change in the Greek tradition came about because at one point in history, the diocesan bishops of ancient sees (which out of the Greek world are pretty much all of them) all came to be styled as metropolitans. Thus, while out of the Slavic and Antiochian traditions, an archbishop is a senior bishop with an honorific title, an metropolitan is a bishop in charge of a major see and thus holding a territorial title. In the Greek tradition, all diocesan bishops (with an few exceptions) are metropolitans by default, and thus an archbishop will be one who holds his title by reason of territory.
The title patriarch is reserved for the primate of certain of the autocephalous Orthodox churches. The first hierarch of the other autocephalous churches are styled metropolitan and archbishop (or some combination).
The primate of the Church of Constantinople takes the title Ecumenical Patriarch. The primate of the Church of Alexandria takes the title Pope and Patriarch. The primate of the Church of Georgia takes the title Catholicos-Patriarch.