Imagine that wifi routers and clients are people standing in a room talking to each other. Every client is friends with one particular router and only wants to talk to that router, and that router only wants to talk to its clients.
A small room with lots of routers will quickly become so noisy that the routers and clients have trouble understanding each other, because other routers and clients keep drowning them out with their own conversations.
One way to fix this is to make the room larger! Then the routers and clients can spread out more and their conversations won't interfere as much.
The new spectrum the FCC is making available, which will be used for 6GHz wifi, is like a really, really big room. Maybe even as big as a baseball stadium or something similarly large. It means that lots more routers and clients can be talking to each other at the same time in more or less the same area without drowning each other out.
Your current phone and wifi router won't be able to support it with just a software upgrade, so if you want to benefit from 6GHz wifi you'll eventually need to buy new devices. But if your current wifi is working fine, there's probably not an urgent reason to upgrade.
How's that for an explanation? 😁