Just trying to educate myself on hubs for a future MacBook Air purchase. Looking at videos on YouTube dealing with Thunderbolt 4 hubs. Don't know why I am looking a Thunderbolt 4 other than that seems to be the latest things; really don't need anything super fast. But I was listening to one commentator talk about "downstream devices". Thought that with Thunderbolt 3,4, and USB C, power and data could go both ways. So do not understand what "downstream" has to do with this. Help?