What do we mean when we refer to Mary's fiat?

What does Mary’s “Fiat” mean, I do not understand the term Fiat and what it means in this sense. Thank you, Mara

The word “fiat” means an official decree or to give sanction to something. In Latin it means “let there be” or “let it happen/exist.” For example, in Genesis when God said “Let there be light” the Latin phrase is “fiat lux.”

The word in common language has become a kind of “catch all” word to describe a permission received or a rule given.

Mary’s response to the angel was a “fiat” statement: “Behold, I am the handmaid of the Lord. May it be done to me according to your word.” Or in Latin: “dixit autem Maria ecce ancilla Domini **fiat **mihi secundum verbum tuum et discessit ab illa angelus”

When we refer to Mary’s fiat we are referring to Mary’s submission to the will of God.