It depends. Children are naturally curious. I think it comes down to how you deal with that as a parent. Our son is interested in pretty much everything we do. As much as possible, we take the time to involve him. Tell him what's happening, why we're doing things a certain way, etc...

I assembled the NFC reader together with him, and he did question what it was for. Obviously he doesn't understand the technical details behind it, but he understand that the box recognizes the cards he put on top of it. That's enough for now. Maybe in the future I can dive a little bit deeper into it.