The Organization Settings screen allows you to configure things at the organizaton level - i.e. things that are not App specific. Examples include:
Whether you will be able to access the Organization settings or what you will be able to update inside them will depend on the Role you have assigned as part of your Organization Membership.
You can access the Organization Settings via the Main Menu in the Top Bar.
The Tabs can be used to switch between different parts of the Organization Settings.
The Close button is used to return to the screen you were previously on.