Neighboorhood bandwidth

Okay. I know a lot less about cable than ADSL but I did work briefly with the technology years ago. So with a disclaimer that I might be a bit woolly in the detail and perhaps well out of date, here goes:
The cable TV system consists of a coaxial cable (or a coax/fibre hybrid) distribution system designed to carry a wideband signal throughout a city or neighbourhood. By wideband I mean there is lots of stuff on there - a traditional TV channel takes at least 6MHz for the video alone and there are multiple TV channels all being sent at the same time, stacked one above the other (in frequency terms) on the cable. The internet provision takes one or more of these bandwidth 'channels' on the system and carries digital data within it instead of TV. At each location a tap device connects a smaller coaxial cable to the main cable to provide service for one or more homes. Then in your home you have a cable modem which is set up to receive the data channel used by your ISP (there may be more than one using the distribution system) and then to give you a particular bit rate within it.
That covers download (traffic into your home) which is the original and main purpose of cable (think TV distribution). As well as the download channels there are several smaller uplink channels (from homes back to the head-end) used for monitoring and control (stuff like pay-per-view for example). Your uplink (from you to the internet as opposed to the other way round) will usually be via one of these.
Hope that helps a bit. For more info have a look at en.wikipedia.org/wiki/Cable_internet and en.wikipedia.org/wiki/Cable_modem
Finally, if anyone can add more detail or sharpen this up a bit I'd be interested too

Thanks for the info. I also saw that my ISP (Comcast) has the ability to cap the bandwidth usage of certain users because at certain times of the day, I get extreme slowness when dealing with any applications that utilize the network.

That could be contention. Effectively, you are sharing your chunk of Comcast's internet connection with a number of other subscribers. If one or more of them, at certain times of day, start heavy downloads then your throughput will drop too. Look around on the internet and find one of the many sites or applications that measure throughput for you (some will even chart it over time) and see how the result varies over say a week. You can then contact Comcast with the evidence and they may be able to figure out who is responsible and cap them

Well, I've used a few tests to measure my times. I've run bandwidth tests through various sites and noticed a significant drops at various times during the day. I've also used this game application called STEAM to test my latency and ping times between me and these game servers. Usually, it reports 80-90 ms return times but occasionally, it returns mixed times of 80-200+ ms times. This causes my game performance to be horrible and my internet browsing performance to be limited at best.

To wrap up this thread,

I spoke with Comcast over 10 times and most recently, I was experiencing horrible latency times when connected to any game server. I managed to get the Comcast Rep to tell me that I'm on a huge node, one of the biggest he's seen, consisting of over 800 users. In my area, he said that the average he's seen is around 500 users per node.

xSaintx,

This site tests your connection speeds:

www.speedtest.net/

I suggest you try it at various times. repeat it for several days. Your results are saved, they give you a URL link to your results. So (as TheBishop suggested) you can give Comcast direct evidence that your speed is really below your committed rate.