Basicaly the snes codes are composed (mostly) from 3 parts for NTSC and PAL regions.
First part indicates the region:
The middle part indicates the code for the game title.
What I figured up for PAL is the following - if the middle part of the code has the 4 characters - the last letter from the code is specific for the language:
The last part of the code (again for PAL regions) can be (specific to the influence regions)
Sometimes there is a number (as a forth part of the code) - it represents the "revision" - it's like the updated version.