A private stream allows the broadcaster to select from a list of their followers as to who they want to share their live streams with, these streams are not public.
You can select all your followers or search and select individual followers. Only those invited will be able to see that you are live streaming and have access to replays. Private live streams are not available to anyone else and will not show up on any views if they are not invited.
All functionality from regular streams are available in private streams including tipping, paid broadcast and deletion of streams.