a. Standard Channels
Note: Files that you share in a channel (viewable on the Files tab) are stored in SharePoint. List of files shared in a channel can be found in the Files tab in a channel.
b. Private Channels
Note: Files shared in a private channel are only viewable by the members of the channel and are stored in the separate SharePoint from the rest of the Team's files.
Private channel meetings and calls
External guests can join a Team's private channel meeting or Meeting now call. During the meeting or call, they'll have temporary access to chat, files, whiteboard, notes, and the participants list (those not in the Outlook invite), but not after the meeting or call.
When you join a new Team, it's automatically shown in your Teams list. If you know you're a member of a Team but don't see it, view your "All Teams" list.