Instead of customizing your character by what spells they can cast, with casting and play style determined by your class, Warlocks choose Invocations, which are essentially magical feats, and develop their play style in that way.
But that begs the question - in a game system where class differences are primarily found through creative setup, rather than playstyle, how do you handle 2 classes that are thematically connected, but differentiated by playstyle alone?
Not really, anyway. They went ahead and built two different classes, for no perceivable reason as far as I can tell. But to make them two separate classes, they had to alter the play style and build between them.
Instead of the normal spell-slots-and-levels setup of other classes, Warlocks get a small number of slots and always cast at the highest spell level, limiting their casting capacity. In exchange, they get more powerful cantrips, spells, and even a variety of martial options, both in the main class features or selectable through Invocations.
As I see many people putting it online, they functionally get two subclasses: Pact and Patron. Plus, they get invocations, which the player gets to choose and change out as they level up, on top of the spells which are inherently customizable. 041b061a72