Since you first started learning about the world, you’ve known that cause leads to effect. Everything that’s ever happened to or near you has reiterated this point, making it seem like a fundamental law of nature. It isn’t.
It is, in fact, possible for an event to occur before its causal factors have manifested or happened. This isn’t how appliances work — you don’t have to worry about will have having left the oven on — but it is how particle physics works. It’s also the key to explaining how time travel, under the laws of quantum physics, could operate.