Marriage for the baptized is a sacrament that is united to the love of Christ his Church, which governs it is the model of the love that Jesus Christ has to his Church (cf. Eph 5: 25-32). There is only true marriage between the baptized when the sacrament is contracted.
Civil marriage is contracted before civil authority. This marriage is not valid for Catholics, the only valid marriage between baptized is the sacramental contracted before a Priest or Deacon of the Church.