The word mystery is derived from the Greek word mysterion.

There are 7 Mysteries that Jesus instituted:

The Sacraments of Initiation (these 3 are given to infants in the Byzantine rite and a solemn Holy Communion is later done at the age of reason):

1.Baptism

2.Chrismation (aka Confirmation)

3.Holy Communion (aka Eucharist)

The Sacraments of Healing:

4.Reconcilliation (Confession, [Act of Contrition,] Penance)

5.Annointing of the Sick

The Sacraments of Vocation:

6.Holy Matrimony (aka marriage)

7.Holy Orders (deacon, priest, bishop)