Action uses shaders to compute the colour, lighting, shadows, and other attributes of each pixel or vertex of objects in the scene.
You can use any media to map textures to Action surfaces and geometries, thus adding detail such as depth and reflections to your 3D composites.
You create maps in Action (such as Diffuse and Reflection maps) based on media from the Media list. To specify different media as the texture source, select the media in the Media menu, then click Apply. If the media you want to use resides elsewhere on your filesystem, you can use the Read File tab of the map menu to load the texture, and then decide if you want the texture to be managed by Action, or not.