There are five options:
Open: any community member can access or join that specific channel.
Private: members need to be invited or added by the admin to see the channel discussions and participate in them. the channel content is hidden from none members.
Paid members: any member on a paid subscription plan can access and join that specific channel. Free members will be asked to upgrade.
By plans: give access channel to channels by specific membership subscription plans. If a member is not on that plan, they will be asked to upgrade their subscription for access.
By segment: give access to a specific channel based on the segment the member is a part of. Only members of the segment assigned to the channel can join and engage with posts in that channel.