This is a kind of 'working space' codec developed by Apple and used in its Final Cut Pro software. It's not designed for final output – instead it's a kind of intermediate space offering much higher quality and 'headroom' for video editing.
It comes in two basic forms: ProRes 422 (with proxy, LT, standard and HQ flavours) and ProRes 4444 (standard and XQ). The numbers refer to the chroma sub-sampling system used (see the next section) and the extra suffix defines the degree of data compression. The extra digit in ProRes 4444 is because it can accommodate an alpha channel for masking/transparency.
You might also encounter DNxHD here, which is essentially video/audio editing company Avid's equivalent of ProRes. Lots of external recorders will let you record direct to ProRes or DNxHD for this reason, so you can choose the format according to the edit suite you're going to use.
Adobe, meanwhile, is seeking to extend the universal DNG raw format it's developed for stills photography into the video arena, with 'CinemaDNG'.
