What do you mean by the two clauses, "Conceived of the Holy Ghost, born of the Virgin Mary"

That He was formed in womb of the Virgin Mary, of her proper substance, to be the seed of David, as had been foretold (Ps 132:11), and yet that this was wrought by the miraculous operation of the Holy Spirit, without the cooperation of a man (Mat 1:18; Luke 1:35).