The benefit of an intermediate codec is that it offers excellent random access performance in post-production applications, and retains higher quality than end-user codecs while still requiring much less expensive disk systems compared to uncompressed video. This is achieved by only using intra-frame compression, where each frame is stored independently and can be decoded with no dependencies on other frames.
ProRes is a line of intermediate codecs, which means they are intended for use during video editing, and not for practical end-user viewing.
