As I understand it, Predestination is a valid doctrine and endorsed by the Church. It means that God, by virtue of sitting outside of time, knows everything that is going to happen to us, given he can "see" our free choices before we actually make them. In this way, although we dictate our futures, we will, in fact, make a choice, and that choice is already known to God. We cannot change what that choice will be any more than we can change a choice we made yesterday (to God, all choices have simply already happened), but we are still free to make that choice tomorrow, just as you were free to choose today, yesterday or 10 years ago.
Predeterminism is a Calvinist form of Predestination (though they use the word 'Predestination' which can lead to circular arguments with non-Calvinists), but the doctrine implies that God makes the decision for us, thereby removing our free will. Simply, He knows all and directs all, according to His will alone. Catholics do not believe in Predeterminism except, if I remember correctly, in rare and special cases where God forces a human decision in order to achieve a goal.
Does that help?
