What is the difference between a diocesan priest and a religious priest?

Answer: 

A diocesan priest ordinarily serves the Church within a rather well defined area (a diocese). He ordinarily serves the people as a parish priest, but he may also be involved in many other forms of ministry: teaching, Chaplain in hospitals, prisons, campus ministry, etc. He makes the promises of obedience and celibacy. The bishop of the diocese is the head of the local diocese. A religious priest, on the other hand, is a member of a community that covers a larger geographic area. They take vows of obedience, chastity and poverty. Their provincials oversees their ministry.