When you create a “paid channel”, we also create a role with the same name as the channel. You can then assign that role to as many other channels as you like. 

For example, you create a “paid channel” called “premium” and when someone purchases they get access to that channel and any other channel that you assign “premium” role as well.

And if you click "paid group" it does not assign a role. It will give and remove access to an entire Discord server.