The Immaculate conception is Mary being conceived free from original sin.
Mary was granted this extraordinary privilege because of Her unique role in history as the Mother of God. That is, She received the gift of salvation in Christ from the very moment of her conception.
When discussing the Immaculate Conception, an important reference is found in the angel’s greeting to Mary. The angel Gabriel said, “Hail, full of grace, the Lord is with you” (Luke 1:28). The phrase “full of grace” is a translation of the Greek word kecharitomene. Since this term is in the perfect tense, it indicates that Mary was graced in the past but with continuing effects in the present. So, the grace Mary enjoyed was not a result of the angel’s visit. In fact, Catholics hold, it extended over the whole of her life, from conception onward. She was in a state of sanctifying grace from the first moment of her existence.
Even though Mary is unique in all humanity for being born without sin, She is held up by the Church as a model for all humanity in Her holiness and Her purity, in Her willingness to accept the Plan of God for Her.
The Solemnity of the Immaculate Conception is a time to celebrate the great joy of God’s gift to humanity in Mary, and to recognize with greater clarity, the truth that each and every human being has been created by God to fulfill a particular mission that he and only he can fulfill.
The Feast Day is celebrated December 8. It is a Holy Day of Obligation.