ELI5: Explain Like I'm 5

supersymmetry

Supersymmetry is a way of describing how particles in the universe work. It says that for every particle there is another particle in the universe that is kind of like its partner. This partner particle is similar to the first particle, but it is slightly different. Imagine if you had a friend who was exactly the same as you in every way – same height, same hair color, same age, etc. – that's what it's like for particles in the universe according to supersymmetry!