The Ghirardi-Rimini-Weber theory is a complicated idea that tries to explain how particles can exist in two different states at the same time, which is called superposition.
Think of it like having two different colored balls in a box. In traditional physics, we would say that the balls are either red or blue. But in the world of quantum mechanics, they could be both red AND blue at the same time.
Now, the Ghirardi-Rimini-Weber theory suggests that when we measure the balls (by opening the box), something weird happens. One ball has to "choose" to be either red or blue, and the other ball becomes the opposite color.
It's like the balls are communicating with each other and deciding which one gets to be which color. This weird communication is called "quantum entanglement," and it's a key part of the theory.
To put it super simply: the Ghirardi-Rimini-Weber theory tries to explain why particles can exist in multiple states at once, and how they "decide" to become one state or another when we measure them.