A proxy is a low-resolution copy of a high-resolution image. There can be one proxy for each frame in a clip. Proxies are used to provide real-time playback of processed results and to supply low-resolution clips so that composites can be quickly created. When importing files as clips with unmanaged media, use proxies when the connection speed to your media storage location is not fast enough to support real-time streaming of the full-resolution media. When proxy generation is enabled, proxies are generated upon import of media.
You can specify how and when proxies are generated for clips in the project settings. See . If you enabled proxies for the project or media resolution, then only the proxies reside in Autodesk storage.