Quantum wave particle duality is a strange idea. It basically means that electrons, and other very small particles, can act both like tiny waves and tiny particles at the same time. It's like getting a super chocolate bar with both chocolate chips and gooey marshmallow mixed together!
Waves can go through each other and mix together, but particles can't do that. For example, if you drop two rocks into a lake, they won't mix together – they just sit there. But if you drop two waves into the lake, they mix together and make one bigger wave.
At the tiny level, electrons and other particles act both like waves and like particles. When trying to understand where an electron is, scientists have to think about it either as a wave or as a particle. It's confusing, but it's true!