For those who have trouble keeping straight in their head whether Moses was before or after Jesus, I offer this brief account of salvation history:
In the beginning (and we mean "beginning" in the broadest sense, the sort of beginning that could span billions of years), God created everything, from angels to galaxies to cockroaches, and as creation's crowning achievement, he made human beings, endowed with intellects so they could know God and wills so they could love God and bodies so they could serve God in the material world. Humanity was to live in union with God. But these very first human beings disobeyed God and did the one thing He asked them not to do: they ate the fruit of the forbidden tree, and bit off more than they could chew. Their bond with God was broken by their own actions. So God banished them from paradise, and thus began the long, sad story of human death and misery. But even then God planned, in the fullness of time, to restore humanity to unity with Him.
Part of God's plan was to form humanity by establishing a special relationship with certain human beings, making covenants with them. He made a covenant with Noah that He would never again flood the entire earth and would no longer make war on humanity. He made a covenant with Abraham that He would bring forth from Abraham a holy people, a people set apart as God's own. He made a covenant with Moses to let Israel flourish in the land He would give them if they obeyed his commandments and laws. He made a covenant with David that David's descendants would rule Israel as a shepherd tends his sheep and always enjoy God's favor. And after the time of David, through the fall of the kingdoms of Israel and Judah, through the captivity of the people in Babylon, through their return to their land, the prophets, from Amos to Isaiah to Jeremiah to Malachi, continually proclaimed God's promises of His covenant, assuring the people that they would one day be fulfilled.
Let's put the contents of these covenants together: God promises to have peace with humanity; God promises to make a holy people; God promises that the people will flourish if they obey Him; God promises that the Son of David will lead this people. God fulfilled all of these covenants perfectly when He Himself came to fulfill them. God took flesh and became man in the person of Jesus Christ, and through his life, death, and resurrection, brought peace between God and humanity, made a holy people of those who believe in him (his Church), gave them the sacraments to give them spiritual nourishment and new life, and became the Good Shepherd who leads his flock.
After Christ's ascension, the apostles spread the Good News of this new and everlasting covenant between God and all humanity, as Christ had sent them to do, traveling to all corners of the known world and building up the Church. (Tradition has various apostles going everywhere from India to Spain to Ethiopia.) The apostles then appointed those who would succeed them in guiding the Church in holiness and teaching the true faith, and those ones in turn appointed successors, so that, two thousand years later, via a sort of apostolic chain of custody, we still profess with the faith of the apostles, and are taught, governed, and sanctified through the work of the apostolic ministry (bishops, priests, deacons).
God keeps His promises.