Quantum entanglement is the term for what happens when two particles are inexorably linked.
"Inexorably" in the sense that even if said two particles are on opposite sides of the galaxy, they will be two parts of the same whole; anything that impacts one of the particles can be found in the other, even if those two particles are separated by a massive amount of space.
It's a weird and paradoxical concept (Einstein called it "spooky action at a distance"), that I don't really understand the physics of and never will because I'm a big dummy that had to read the simple version of Wikipedia first to get my head around the idea of it.