I’ll bite. What’s the difference?
Canonically, secular is any person who is not consecrated. Lay people are seculars. Diocesan priests and diocesan deacons are also secular men. Members of certain orders are also secular.
Consecrated are those who make vows as religious: brothers, sisters and nuns. Sometimes you will have priests who also join religious orders. They make vows. They cease to be seculars and are henceforth consecrated brothers, even though they are ordained. Many religious communities admit priests among their ranks, provided that there are not given any special privileges or rights because they are ordained.
Secularity is that which is proper for the person who is not consecrated, even if he is a priest or a deacon. This person has rights and duties in the secular world that the consecrated do not have. For example, a secular man or woman, whether he is a priest or not, belongs to a diocese. He has the right to own property, make money, determine his own life, participate in the affairs of the secular world. He also has the right to have opinions of his own. He determines how he or she will live the Gospel according to his state in life: ordained, married or single. He has a mission to make Christ present in the secular sphere. That may be at work, in his community, among his family and friends. Unless he has made a promise of celibacy, he has the right to marry and have children. With this comes the duty to raise a Christian family. He also has a moral duty to influence government and business according to the laws of the Church. This is the biggest difference between secularity and secularism.
Secularity, means that because a Christian is a secular man he has a moral duty to influence the political enviornment to bring it into compliance with the teachings of the Church. For example, we have elections coming up. Secular Catholics, including secular priests and deacons, have a moral duty to vote according to the mind of the Church, not the mind of the state or the national constitution. To vote according to the mind of the state or the national constitution is secularism, because it places the secular vision of the world and of government over the vision of the Church and the Gospel. In the USA we have many people who believe that they must support certain government decisions and policies, because we have separation of Church and state or because not every American is Catholic. This is secularism. This is in conflict with Cathoicism. The national philosophy never trumps the teachings of the Church, even if those teachings are not ex-Cathedra. Because they come from the authority of the Church, they must always precede the state and must govern the choices made by the secular man and woman.
The consecrated person, is not a secular person. Therefore, he or she does not participate in the affairs of the secular world, unless he is ordered to do so by the Church or by his religious community. Like the secular Catholic, when he or she does participate in an election (for example), he must represent the mind of the Church and safeguard the moral order according to the teachings of the Church and of the founder of his or her religiuos community.
Another difference is in the area of personal decision making, personal opinions, wishes, desires, hopes and plans. The consecrated peson forfeits these rights. He surrenders them when he makes his or her vow of poverty. He or she no longer owns his own will. Therefore, he obeys, even when authority is wrong. He has a moral obligation to obey under penalty of grave sin, which can lead to excommunication and dismissal, not always. He may only disobey if he is commanded to do something that has been defined as a sin. It cannot be something that he or she believes is a sin. What he or she believes is irrelevant. Those of us who are consecrated religious, do not enjoy the freedom of secularity. Therefore, we do not enjoy the freedom to act according to our opinions, wishes or personal goals. We do not aspire to own anything, to get ahead in society, to have families (we already have a family, our religious family), we do not even belong to a diocese. We are homeless. When we make vows, we give up our rights as members of the diocese in which we were baptized or in which we live. It’s called excardination.
Both the secular and the consecrated have a duty to avoid secularism or better said, we have the moral duty to avoid any way of thinking, acting, choosing, speaking, working or living that would exclude God and the teachings of the Catholic Church. But as I said above, the secular has the moral duty to work in society to bring society into conformity with the Church, not the Church into conformity with society. The Church chooses where and when she will conform to society, the faithful do not do that for her.