What is the difference between what you call a Secular Priest and a Religious Priest?

The Catholic Answers

In the Catholic Church there are two vocations open to a man who feels called by God to His service. Either he will feel called to be simply a Priest, or else, in addition, to enter a Religious Order. If called to be a Priest, he enters college and is prepared for parish work, in which he must provide for his own necessities. This involves the necessity of income from which he can save enough to provide for possible years of sickness, or later years of retirement. If called to a Religious Order, he takes a vow of poverty, renouncing all personal income, the Order providing his necessary food and clothing. Both types give their lives to God, but in different ways, according to their different vocations. The former are called Secular Priests, because they must live alone in the world; the latter are called Religious Priests, because they live in Religious Communities. Secular Priests are not worldly Priests, Order men only being religious Priests. A Secular Priest could be a far more religious man than an Order Priest, and many an Order Priest is greatly edified by the Secular Priests he meets. It is simply a question of different types of vocation.

Radio Replies Volume 1 by Rev. Dr. Leslie Rumble MSC and Rev. Charles Mortimer Carty