You can use image files for various purposes: textures to control surface color, texture maps to control other attributes, rotoscopy, compositing and other effects in the Fx Tree, and so on.
Softimage uses sources and clips to manage these images:
A source is mainly a reference to the path for an image file or sequence on disk. An image source is not really a usable scene element. It is defined as read-only and is listed in your scene in the Sources folder of the Scene Root. Image sources can reference files within your project, or outside of it.
A clip represents an instance or use of that image in a scene. You can define multiple clips from the same source, and apply different settings to each one without affecting the original source image. Alternatively, you can reuse the same clip in different textures and other properties.
Clips are useful because they allow you to create different representations of the same texture image (source), such as five different blur levels of the same source image. Also, clips are memory-efficient because the source is only loaded once, regardless of the number of clips created from it.
