I wish you all a most blessed Feast of the Holy Trinity, the One and Only True God in Three Persons: Father, Son, and Holy Ghost!
The dogma of the Holy Trinity is the most fundamental dogma of the Catholic Faith.
The Son proceeds from The Father by Generation. The Holy Ghost proceeds from The Father and from The Son as from a Single Principle through a Single Spiration. These two processions are eternal, that is, having no beginning and no end.