mystery of saints (st.)?

Question

Why is the word st. is written before some people's name?Who was the first person to have st. before his name?What is its significance.please explain me the mystery of saints.Who are st.?

Answer 1

There are over 10,000 named saints and beati from history, the Roman Martyology and Orthodox sources, but no definitive "head count".
How does the Church choose saints?

Canonization, the process the Church uses to name a saint, has only been used since the tenth century. For hundreds of years, starting with the first martyrs of the early Church, saints were chosen by public acclaim. Though this was a more democratic way to recognize saints, some saints' stories were distorted by legend and some never existed. Gradually, the bishops and finally the Vatican took over authority for approving saints.

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Answer 2

In the Orthodox church which was founded in the year 33 by Jesus Christ a saint (from Latin, sanctus) is one who is holy, that is, set apart for God's service. It is a person who has cooperated with God's grace to the extent that his or her holiness is beyond doubt.

Aside from the more general use of the word saint to refer to all members of the Church, Holy Tradition also ascribes Saint as a title to particular persons whose lives have shown most clearly what it means to follow Jesus Christ. These saints are popularly glorified (canonized) by the Church, often in the modern era with a formal service to recognize and affirm the veneration of them by the faithful.
Saints are not thought of as perfect, and it is only because of the work of Christ in them that the Church praises these people. It is because we see our Lord's countenance reflected most clearly in their faces that we publicly laud them, ask them to pray for us, and encourage one another to follow their examples.

The people of the church do not create saints, they recognize as saints those whom God himself has glorified, seeing in their lives true love for God and their neighbors.
From the beginning, the Church recognized the righteous ancestors of Christ, forefathers, as grace-filled men and women whose lives were pleasing to God. Also the prophets who predicted Christ's coming and the apostles and evangelists who proclaimed the Gospel were assumed to be saints.
Next the martyrs and confessors who risked their lives and shed their blood in witness to Christ were also recognized as saints.
In time, ascetics who followed Christ through self denial, were numbered among the saints.