What are the duties of the monks?

Answer 1

The duty of a monk is to pray.

Particularly the monk chants the Psalms in what is called the Divine Office (Work of God).

A typical traditional Catholic monastic prayer day looks like this:

3:30 AM Vigils (12 Psalms)

then about an hour for private prayer

6:00 AM Lauds (Morning prayer, 5 Psalms)

7:30 AM Prime (3 Psalms)

9:00 AM Tierce (3 Psalms)

9:30 AM Holy Eucharist

12:00 PM Sext (3 Psalms)

3:00 PM None (3 Psalms)

6:00 PM Vespers (Evening Prayer, 4 or 5 Psalms)

7:45 PM Compline (Night Prayer, 3 Psalms)

Of course, each monastery has it's own prayer schedule... the one above is just typical for traditional monasteries.

Besides public communal prayer (Liturgy) the monk also is called by his vocation to UNCEASING prayer (Prayer of the Heart). It is a continual remembrance of the presence of God, a continual (sometimes sub-conscious) awareness of God's loving presence and protection... A continual attitude of Adoration and Worship... this is the job of the monk.... to make his heart a continual sacrifice of Praise to God the Father, through Jesus Christ, in the Holy Spirit.

So, PRAYER is the one work of the monk.

Answer 2

Monks are men who take Holy Orders. They devote their life to God and endeavour to do his will on earth. Usually this means praying and charitable works such as helping the poor, sick and needy in places like hospitals - this is where we get the word "hospitality" and "hospitable" because hospitals were not just places for the sick they were places where poor people, pilgrims and travellers could stay. It is also why in hospitals senior nurses are still called "sister" because in the past senior nurses where nuns and the abbess or "mother" was the head of the hospital or "matron".

When men become monks and women become nuns (taking Holy Orders) they swear solemn vows (promises) of poverty, chastity and obedience.