When I was a child I used to ask my mother what happened to people who weren’t Christians when they died. She always said, “That’s between them and God.” I understand this as meaning that while I am assured of my own salvation, being faithful to Jesus Christ, if I extend that offer of blessing to others and they refuse it, they’re on their own. When they stand in front of God at the end of their lives, perhaps He will have mercy on them, perhaps He won’t. The difference is that while we are promised our eternal life in heaven, they are not and we can’t know with any certainty what will happen to them.
It’s sort of like this. Imagine a bullet-proof vest. If you get shot in the chest while wearing your vest, you will not die; the vest will protect you (assuming it’s the world’s most perfect vest). You recommend to others to wear the vest as well, and those that refuse get shot in the chest as well. Will they survive? Will they not? We don’t know, but we know that we are safe.
Is this what the Catholic Church is referring to when it speaks of salvation?