what is the anointing of the infirm?

By the sacred anointing of the sick and the prayer of the priests the whole Church commends those who are ill to the suffering and glorified Lord, that he may raise them up and save them. and indeed she exhorts them to contribute to the good of the People of God by freely uniting themselves to the Passion and death of Christ. (Catechism of the Catholic Church paragraph 1499)

When is this sacrament offered?

Anointing of the Infirm will take place after the Sunday Masses on the second Sunday of each month.

who should recieve the anointing of the infirm?

The Anointing of the Sick "is not a sacrament for those only who are at the point of death. Hence, as soon as anyone of the faithful begins to be in danger of death from sickness or old age, the fitting time for him to receive this sacrament has certainly already arrived."

 from the Catechism of the Catholic church:

The Church believes and confesses that among the seven sacraments there is one especially intended to strengthen those who are being tried by illness, the Anointing of the Sick:

This sacred anointing of the sick was instituted by Christ our Lord as a true and proper sacrament of the New Testament. It is alluded to indeed by Mark, but is recommended to the faithful and promulgated by James the apostle and brother of the Lord.

From ancient times in the liturgical traditions of both East and West, we have testimonies to the practice of anointings of the sick with blessed oil. Over the centuries the Anointing of the Sick was conferred more and more exclusively on those at the point of death. Because of this it received the name "Extreme Unction." Notwithstanding this evolution the liturgy has never failed to beg the Lord that the sick person may recover his health if it would be conducive to his salvation.