The UI element is shown in 3D space, as defined by its position, rotation, and scale.
The UI element is shown in 2D on the screen at its position. Rotation and scale are not used, the size on screen corresponds to the size of the UI element. UIElement.useTransparency does not have an effect, screen UIs can always be partly transparent. Screen presentation is not possible in VR, and the UI will fall back to ViewAligned for VR players, so make sure to set an appropriate scale even when using screen mode.
The UI element is shown at its position and with its scale. Rotation is not used and instead the UI is always facing the camera
Presentation style for UI elements, used for UIElement.presentationStyle