Teams - Channels and Teams first things to know.

When you first use Teams there is a tendency to create lots of Teams which can be difficult to manage, you should be looking at creating channels within the Teams to reduce Teams size and improve the manageability. I think of a Teams as a house and each room in a house is a channel- some, which everyone can enter and some can be Private- you can made a channel exclusive to certain members of the Team (household), but you must be a member of Team. So if you have entry to a House you can enter the rooms if allowed.

Here is Microsofts explanation:

https://support.microsoft.com/en-gb/office/first-things-to-know-about-teams-and-channels-5e4fd702-85f5-48d7-ae14-98821a1f90d3