The 3D View shows the 3D model under lighting conditions which helps look at how the surface material is defined. This is also where it is possible to directly paint over the 3D model.
At the top left of the viewport may appear a text indicating the currently loaded profile. For more information see the Color Profile page.
If the 3D model file used to create the project or import the mesh has cameras defined, they can be imported into the project and used to change the Camera location and orientation. This dropdown allows to switch between the camera available in the project. If there is no other camera than the default, the dropdown won't be displayed.
By default the viewport display mode is set to material to show the environment lighting. The dropdown allow to switch the display mode to solo which isolate channels and mesh maps individually.
At the bottom right of the viewport is the 3D view axis which indicates how the scene is oriented in comparison of the camera.
The viewport display can be affected by other settings: