Imagine being at a dinner party with your aunt, and you can't quite remember if she's wearing a blue or green dress. But, you're pretty sure she's wearing something that's definitely not black. That's basically what Werner Heisenberg said: you can never know for certain, but you can be pretty sure-ish. It's like, quantum, man!
Learn more about Schrödinger Cat and how it relates to Heisenberg's principle of uncertainty.
Or, if you're feeling adventurous, explore the wibbly-wobbly world of quantum mechanics.