Hail Mary
Ave Maria
A greeting woven from Scripture — the angel Gabriel's words and Elizabeth's blessing — asking Our Lady to pray for us.
Hail Mary, full of grace, the Lord is with thee. Blessed art thou amongst women, and blessed is the fruit of thy womb, Jesus. Holy Mary, Mother of God, pray for us sinners, now and at the hour of our death. Amen.
Origin
From Scripture (Luke 1) and the Church's tradition
When to pray it
Anytime — the building block of the Rosary