Whenever a member of your organization joins Quip Business, they will be added to your organization's Group folder. Any documents and folders in this Group folder will be accessible by the members of your organization.
If you have documents on your Desktop that are not in a shared folder, they are private to you. No one else in your organization will have access to those documents, unless you explicitly share them.
If you want to create a private folder within your company's shared folder, you can create a restricted folder. You can then manually add other team members to the folder. This feature is particularly useful for creating departmental sub-folders and workspaces