By default, new scenes do not contain light sources.
However, default lighting in Maya LT helps you to visualize objects in Shaded display in the Scene view (press 5). If you turn default lighting off and have no lights in the scene, the scene appears black.
If you bake a scene without a light, Maya LT creates a directional light so that your objects can be seen. Without it, your objects would not be illuminated and the preview would be black.
This default light is parented to the rendered camera. The entire scene is illuminated no matter where the camera is facing. The surface areas directly facing the camera are bright while the surface areas hidden from the camera are dark. This provides surface contours that look realistic.