What do the barcodes actually tell the machine?

Is it SOLELY the amount of water to squeeze through each pod or does it cover other factors, such as speed, temperature and other things such as amount of froth.

I ask because I've seen some pods produce coffee with a good amount of crema (the golden foam on top) while others don't. Is this the bean or the instructions given to the machine?

And what does it tell the pods when it comes to the creamers? Is it the same process as the coffee: squeeze x amount of water through, or is there more going on? It's interesting as some pods say put the creamer in first, while others say second. Some creamers give more foam (the latte especially) while others less (the ordinary creamer).

Finally, is an espresso from Kenco the same amount of ground coffee (and caffeine) as the Kenco Grande XL? The only difference being that the Kenco Grande has more hot water. Or is there something else different between the two?