“At the quantum scale, particles can also be thought of as waves. Particles can exist in different states, for example they can be in different positions, have different energies or be moving at different speeds. But because quantum mechanics is weird, instead of thinking about a particle being in one state or changing between a variety of states, particles are thought of as existing across all the possible states at the same time. It’s a bit like lots of waves overlapping each other. This situation is known as a superposition of states. If you’re thinking in terms of particles, it means a particle can be in two places at once. This doesn’t make intuitive sense but it’s one of the weird realities of quantum physics.”
Superposition featuring Schrödinger’s cat:
“When we are not looking, the world is acting completely crazy. But as soon as we turn around, it pretty much acts as normal.”
“The superposition principle claims that it [an electron] has many positions while we are not looking at it. […] When you didn’t see how something happened, then it happened in all possible ways.”
– See also Get Entangled! On Positions and Momentums.