Hi, all experts. Just a stupid question as below:

I just bought a video module for my 12/2000 made x5 which is an older version than the damaged one used in my car. I found that the one I bought was a bit different with my original one which is that there is a big plug hole on the back of the module. My original one which is damaged does not have the big plug hole. Just want to know what the big plug hole for? I searched in the internet, someone said the hole is for CAN bus, what is CAN bus? Someone told me that the module I just bought was for e38 origianlly. Just wonder if the one for e38 is the same or compatible with the one for e53? Can I use it on my e53? Thanks for any input. Please help me, experts!

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--2004 E53 X5 4.8is - ECE version; right hand drive; Located in Hong Kong; ext. black sapphire metallic; int. leather black; adaptive dynamic bi-xenon headlights; 16:9 onboard monitor w/o navigation; 20" genuine BMW Y-spoke 214 wheels with Bridgestone Dueler H/P Sport tires; Int. rear view mirror w/ compass.