Software vs. bandwith

I'm in the medical field so excuse my lack of knowledge. I have a basic knowledge of hardware and absolutely Zero knowledge when it comes to software. Anyways, when people talk about bottlenecks occuring, it's hard for me to comprehend how this happens. Say we're talking about 6 Gb/s being a bottleneck. The code for a whole game can be 6 Gb worth of harddrive space. I understand that running a game at 1600x1200 with all the effects on in addition to AI and anything else that can happen is alot of information. But still it's the analogy that gets me: the bandwith being equal to a whole game's worth of code in a second. And i'm assuming since we are only dealing with 1 second's worth of game, a very small percentage of the actual gaming code is used--this must speak greatly for coding efficiency. I guess I would need to take a few classes concerning software to begin to even understand this but if anyone has an 'answer for dummies', I'd appreciate it.

Yeah thanks. I guess I missed that bandwith was being measured in Gb instead of GB. Still an impressive amount of info to be shuffled around.