Premium members can set their channel as "private stream". If you stream live your channel won't be listed on our website. Nobody can enter your stream, as long as they don't get the unique URL to your channel. So you can decide who is allowed to watch your live stream and who isn't.
It's useful for paid workshops, Patreon pledges and to stream only among familiar faces.
You can always turn private mode off, so your channel gets public again. But don't post your private mode URL publicly on social media etc. otherwise your private mode will lose it's privacy.