Just what does Catholic mean?
Catholic means universal. Jesus founded One Church, his Bride. As one wise priest said: "Jesus has one Bride, not a harem!"
All those baptized "in the name of the Father and of the Son and of the Holy Spirit" belong to Christ and his Church. Over the centuries some brothers and sisters have broken fellowship with the "Mother" Church- that is, the Catholic Church, and formed gatherings whose members, although they are not in full communion with the Mother Church, are still Christians- brothers and sisters in Christ. We invite our brothers and sisters in these gatherings to "come and see."
What exactly is a sacrament?
When you see a book labeled "The Holy Bible" you know it contains nourishment for your soul. You must pick it up, read it, meditate on it. The Bible is a sign of what God can do for your soul.
A sacrament is a little bit like that. Sacraments are outward signs of an inward working of God's grace. They have the power to do exactly what God intends them to do. I can see you pick up a bible and read it, but I cannot see the good it may do for your soul. We can see the outward signs of sacraments- water, oil, bread, wine, but we cannot see the action that God takes upon the person's soul.
This analogy is not perfect and there are many more important aspects to the sacraments. Perhaps the most important is that the Bible can inspire you, but it cannot impart to you the grace to do what it says. A sacrament does just that! It actually gives you the grace to love, forgive and walk the way of Christ!
Like picking up and reading the Bible in order to receive its benefits, a Catholic must cooperate with the sacraments for them to bring an effective work of grace in their souls. The grace from the sacrament is in your souls waiting to assist you in every way to salvation.