There are a couple of builtin viewports, that each do different things. Here is a list of the names, and their descriptions:
| Viewport Name | Description | 
|---|---|
| StretchViewport | Will stretch the screen. No black bars, but aspect ratio might be off. | 
| FitViewport | Will maximize it's size based on the aspect ratio. Could have black bars. | 
| FillViewport | Quite the same as a FitVieport, but always fills the entire screen. | 
| ScreenViewport | Always fills the entire screen, but does not resize any children. | 
| ExtendedViewport | Keeps the world aspect ratio without black bars by extending the world in one direction | 
| CustomViewport | A custom programmed Viewport. Might have black bars, and might keep aspect ratio. |