As Catholics, we believe our life doesn’t end at death but simply changes. Those who have lived good lives and died in the faith of Christ will share in His Resurrection. While we live together on earth as Christians, we are in communion with one another. But that communion doesn’t end when one of us dies. We believe that the saints — the Christians in heaven — remain in communion with those of us on earth. We call this the Communion of Saints, and it’s an article of faith in the Apostles’ Creed.
When we run into trouble in our lives, we frequently ask friends or family to pray for us. We know God hears their prayers as well as ours, and we want as many voices as possible asking Him to help us in our time of need. So, we pray to the saints and angels in Heaven because they stand directly before God and offer Him their prayers. And since we believe in the Communion of Saints, we can ask the saints to pray for us, just as we ask our friends and family. And, when we make such a request for their intercession, we make it in the form of a prayer.