File in Microsoft Teams with permissions?

Solution 1:

It’s important to remember that the “Files” tab is available and that it’s mandatory for each channel in a Team to be connected to file storage in SharePoint. Files for each channel are stored in a folder in the document library of the SharePoint site that supports each Team.

Owners and Members have the ability to share rights to any files or pages–the entire site collection, even–to anyone in the organization. This means that any files stored or shared inside a Team are subject to the sharing and permissions rules of SharePoint.

In addition, the files in private chats are stored in the One Drive For Business of the users that upload them in a “Teams Chat Files” folder before being shared with others in the chat.

Credit to Hunter W.