Unlike many other ARPG's like Diablo II or Path of Exile, Last Epoch allows for unlimited class customization options.
When you first start out, you pick from one of only a few different class options, which is normal for any game like this. But as you start to level up character, you can pick and choose subclasses to expand your character's strength.
As you can see, the character above started out as a Mage and after some time, I began exploring in the realm of being a Sorcerer. Probably the best thing about this system is that each subclass has its own passive skill tree as well as new spells to be learned.