When you create a new team, the first thing to define, aside from its name, is its type. There are three to choose from: Open, Closed and Secret. This setting will define what level of visibility and access each team has within your organization's Figma account.
Visibility: Everyone within your organization can see the "open" team listed, join it, and see all of the projects or documents inside.
Permissions: Members who choose to join an open team will be given view access (with the ability to comment, inspect and export assets) by default so they can't accidentally edit something. Team admins can grant edit access to the team to individual people as necessary.
Good for: Companies that want to foster a highly collaborative environment. When people have a window into what other teams are working on, they have the opportunity to work more cross-functionally and they can maintain consistent patterns across different products or projects.
Visibility: Everyone in the organization can see that the "closed" team exists from the "View all teams" modal, but non-members will not be able to immediately see or join the projects and documents inside.
Permissions: Users who wish to join a closed team need to request access to see projects. Team admins can permit or deny these requests and give the users the appropriate amount of access (view or edit).
Good for: This type will be best suited for teams who can't share their work with the entire organization, but can still benefit from everyone knowing about their existence. This gives people a destination to go if they do require access.
Visibility: No one can see that a "secret" team exists within the Figma organization, unless they are the creator or have been specifically invited to join.
Permissions: Owners of secret teams need to individually invite the members they want to have access. They can also set the appropriate view or edit permissions for each user.
Good for: This is great for top secret projects that only a very specific subset of users require access to. Think of work done leading up to an acquisition or something that cannot have org-wide knowledge. This access type can be changed at any point to give these teams more visibility when the timing is right.