Catholicism = Christianity
Christianity = Catholicism
These terms are synonymous
Protestantism = heresy, just another of dozens that have been and are no more, which is what it is destined to be, because truth will win out over falsehood
Protestants are Christians, but they are heretical ones
Orthodoxy = schismatic
I think of it like a tree. Christianity is the tree, grown from the seed who is Jesus, who “fell upon the ground and died”, was raised from the dead, and now bears much fruit. He filled the tree with His Life, who is the Holy Spirit, the sap of the tree. Orthodoxy is a large branch, almost like another trunk, that started growing about halfway down. It grows, but not vigorously, because there was disease at the root of it. The other branches and leaves of the tree have grown far above it. Soon (relatively speaking - we are talking about the growth of plants), the Gardener will mend the connection. Protestantism is a sickly branch that sprouted near the top. That branch has itself branched many, many times, but it bears little fruit, since it is more like a thin, vigorously branching sprig, than a branch. The little life it has comes, of course, from the tree, which is Christianity. Sometime in the 20th century it began to wither and will soon die. I think the Gardener has had enough of it. He wants all people to be leaves on the one healthy tree. So the “leaves”, if you will, will become attached to the branches of the tree again, the barren branch will die and fall off, and there will be much rejoicing. Around the base of the tree are all the dead branches that had sprouted, mostly near the base of the tree, but soon died and fell off. They are now only a matter for the history books. There are other plants around. The closest ones to the tree are a very large bush with two main trunks and a small bush. They did not sprout from Jesus, but were planted by another who shall remain nameless. Some say angels uprooted the seed who is Jesus and re-planted the tree, but it is not so. The “good seed” could also refer to the Word of the seed, the Kerygma or Gospel. Most of the other plants just sprang up by themselves. These other plants are destined to die as well, for all will be one, as the Father, Son, and Holy Spirit are One. There is only one table at the one wedding supper of the Lamb.
That’s not to say that there aren’t many good and holy Protestants and Orthodox, Mormons and Muslims. On the contrary. I’m talking about the branches, not the leaves. For example. Protestantism would be a branch, individual Protestants would be the leaves on the branch. There are many good and beautiful leaves and flowers on all the plants in my analogy. God is good and he gives His grace to all, even outside of the means He knew and designed in eternity and established at His Coming. He always draws good out of evil, starting with the fall of Lucifer and then Adam.
That’s the way I look at it, anyway.