Teams - Private Channels and SharePoint
This article provides information about Teams Private Channels and how their associated sites work.
Each private channel has its own SharePoint site. The separate site is to ensure access to private channel files is restricted to only members of the private channel. These sites are created with a document library by default and can be easily enhanced to a full-featured site through the site management interface.
A private channel site syncs data classification and inherits guest access permissions from the site of the parent team. Membership to the site owner and member groups are kept in sync with the membership of the private channel within Teams.