The Immaculate Conception, was the conception of the Blessed Virgin Mary in the womb of her mother,Saint Anne, free from original sin by virtue of the foreseen merits of her sonJesus Christ.
Mary was conceived by normal biological means, but God acted upon her soul (keeping her “immaculate”) at the time of her conception.
The Immaculate Conception is commonly mistaken to be the conception of the Child Jesus in her own womb and the Virgin Birth of Jesus but the Immaculate Conception deals with the conception of Mary herself, not that of her son.
These are covered by theDoctrine of Incarnation.
Although the belief that Mary was sinless and conceived immaculate has been widely held since Late Antiquity, the doctrine was not dogmaticallydefined until 1854, by Pope Pius IX in his papal bull Ineffabilis Deus.
The Catholic Church celebrates the Feast of the Immaculate Conception on December 8; in many Catholic countries, it is a holy day of obligation or patronal feast, and in some a national public holiday.