Hey - so I've a bit of a newbie myself but, like you, I started looking at this stuff and also found it super confusing (I'm actually surprised Lego's marketing team chose such a disjoint approach).
So here's what (I think) I've gathered so far:
- "Powered up" is the name of the family of hardware, which includes all the hubs, motors, and sensors from this line.
- Spike, WeDo, and Boost are specific lego sets that are tied to their own respective apps. They use subsets of the Powered Up family of hardware (i.e. there is a WeDo hub that is part of the Powered Up family,and there is a Boost hub that is also part of the Powered Up family).
- There is a "Powered Up" app that can control all Powered Up hardware, including the Powered Up hardware used for Spike, WeDo, and Boost.