Answer
Under the Family Code, a valid marriage requires both essential and formal requisites. The two essential requisites are (1) the legal capacity of the contracting parties, who must be a male and a female, and (2) consent freely given in the presence of the solemnizing officer (Article 2). The three formal requisites are (1) the authority of the solemnizing officer, (2) a valid marriage license (except in marriages exempt from the license requirement), and (3) a marriage ceremony in which the parties personally declare that they take each other as husband and wife before the solemnizing officer and at least two witnesses of legal age (Article 3).
The absence of any essential or formal requisite generally renders the marriage void from the beginning; a defect in an essential requisite makes it voidable (annullable); and a mere irregularity in a formal requisite does not affect validity but makes the responsible party liable (Article 4).