The Archbishop of York is the head of the Northern Province of the Church of England (and previously for the Roman Catholic church that preceded it, of course). He is merely the Primate of England and plays second fiddle to the Archbishop of Canterbury, although he retains jurisdiction over the diocese to the north of the Humber. (Which at one time included the dioceses of Scotland as well.)
When Pope Gregory sent Augustine over to Britain to convert the pagan Germanic warlords who had conquered much of old Roman Britain, it was always apparently his intention to create two separate archbishoprics at Canterbury and York, but this was never put into effect. The first names on the list, from Paulinus to Wilfrid II were therefore mere bishops, with Egbert, brother of king Eadberht of Northumbria being the first real archbishop.
The Bishops and Archbishops of York to date
Paulinus was the first but deserted his post in 633 when York was occupied by Cadwallon ap Cadfan and not until 644 was a replacement appointed. In general, the succession in the period before the Norman conquest is often uncertain, hence the odd gap here and there.
Sourced from the Archbishop of York online at http://www.bishopthorpepalace.co.uk/archbishop.html and the Catholic Encyclopedia