Net Carbs: What it Means

I'm sure, like other people, the term "Net Carbs" is familiar, but slightly confusing. I mean I see that the companies with subtract the fiber from the total carbohydrate number, and come up with a lower number, which allows them to advertise their product as low carb. I needed to know where the logic came from though! So here it is.
Carbohydrates are made up of sugar, fiber, and starches (you don't usually see this one on the nutrition label). Only the sugar and starches actually affect your blood sugar levels, because sugars and starches get converted to glucose. Fiber does not get converted to glucose. It hangs out in your gastrointestinal tract, and keeps things running smoothly, if you know what I mean.
So net carbs is the amount of "available" (i.e. available for energy) carbohydrates. This is why eating high fiber foods helps with dieting. Fiber makes you feel fuller, because it still goes to your stomach, but it is not available to be converted to fat!
I hope this helps anyone who was confused. I was suspicious of these food lables, so I just had to make sure!