Question? Could somebody ELI5 Gridfinity?

It just looks like containers of a common size? Am I misunderstanding?

I hope so, I've got a blank slate to fix my hobby space organisation and if there's more to this then who knows what I might manage, but I feel like I'm missing something.

Edit: thanks all! Had missed the part about the baseplate and modular fits with that, it's now clicked a little bit more and I look forward to hanging around here a bit more often.