Predestination was an idea invented by John Calvin in 1536(Calvinist Heresy). It says that everyone is either going to Heaven or Hell already when they are born, and there is nothing we can do about it. But Jesus says, I will forgive you your sins (Colossians 1:14) which means you can get out of going to Hell.
You might say that technically if God forgives everybody, then everybody goes to Heaven so Calvin was right. But that is not true, because God does not forgive some sinners, like pagans and foreigners.
Predestination is also called unconditional election, the U in the TULIP mnemonic for the doctrines of Calvinism.
Calvinists sometimes cite Ephesians 2:8-9 in support of predestination:
- For by grace are ye saved through faith; and that not of yourselves: it is the gift of God: Not of works, lest any man should boast. (KJV)