The feast of the Immaculate Conception is a religious festival that is celebrated on December 8. It is a day that celebrates the belief that celebrates the conception of the Virgin Mary in the womb of her mother, Saint Anne.

Source : wikipedia.org
It is a holiday that is often confused with the Annunciation of the Lord, a day that celebrates the appearance of the angel Gabriel to Mary and her willing acceptance of accepting the conception of Jesus Christ in her womb. In general, it is considered one of the most important Marian feasts celebrated in the liturgical year of the Roman Catholic Church.
History
The Feast of the Immaculate Conception dates back to the fifth century when it was first introduced in Syria. In the seventh century, this festival was already firmly rooted in the tradition of Eastern Christianity.
Although the Immaculate Conception was firmly rooted in the Christian tradition, there has been much debate about what the term really meant. When it arrived in the West, towards the eleventh century, a lot of controversy was generated around the subject. While both Eastern and Western traditions hold that the Blessed Virgin Mary was free from sin throughout her life, people did not agree with what this really meant.
St. Thomas Aquinas argued that the Blessed Virgin could not have been “redeemed from original sin” if she had not been subject to it in her conception. However, other theologians did not agree with this position and believed that it was indeed possible.
The problem was solved when Duns Scotus defended the Immaculate Conception. After that, the party spread through the western church. In 1476, Pope Sixtus IV introduced the doctrine completely into the Western Church and threatened anyone who opposed it with excommunication. Eventually, the controversy that surrounded this party would be extinguished and by the middle of the seventeenth century it was accepted as a doctrine by almost everyone.
Today is an Obligation Day and is celebrated with a Holy Mass. It is also celebrated with family events, processions and parades dedicated to the honor of the Virgin Mary.