[Alkhin]

I dont know that a priest is required to join a particular order.

[Integrityrocks]

I dont know that a priest is required to join a particular order..

Besides that there are hundreds of orders to choose from, the other option is being a Diocesan priest. That is not an order.

[ZULU]

Yeah. A priest is ordained as a Secular Priest, or as a member of a "Regular" order, e.g. Benedictines, Augustinians, Carthusians, Jesuits, etc.

I wondered about whether he was ordained a Benedictine, as according to the prophesies of St. Malachy, he might be a Benedictine.

[SolomoninSouthDakota]

"I don't know that a priest is required to join a particular order."

There are two main categories of priests--diocesan and order priest. Basically, diocesan are organized structurally by region in dioceses ( a geographical area). Most folks associate "priests" with the diocesan priests.
But there are also "orders" of priest's (such as the Benedictines) that are formed into groups based on a non-geographical border. They group more along a "type of spirituality (charism). (Benedictines are associated with great teaching and give the Jesuits a run for their money.)
These orders have a "command structure" apart from the diocesan system. They don't answer directly to a Bishop, but to their order's Superior who answers to the Vatican directly. The current pope, I'm quite sure has always been a diocesan priest. (They can switch with permission.)
An interesting aside is that their were no diocesan priest named "Saint" until St. John Vianney, the Cure de Ars (France).