Basically what happens with the Bandwidth thing, to explain it differently...
images are basically a bunch of code. By putting an address inbetween the img tags, essentially this is what happens.
The picture shows up here. But in order to get that picture here, the Knitting Help. com has to find that code. It looks in the tags, and discovers that the code for that picture is still over on the other computer. So the KH servers go to the other computer servers and grab the code from them.
Another way to talk about Bandwidth is to say it is like paying for advertising on t.v. Every time someone looks up your webpage, you've used up one of your credits.
So the KH server's have used up one of the other webpage's credits. This can really anger some people because they don't want you looking at their pictures without there being something in it for them.
And it can also anger the people whose's server's have to spend time going to go and get that code. Although you often won't notice it, it will take longer to get that picture. And you are causing the computers to have to take more time to do a task that really would take much less time if the code for that picture was on the KH server in the first place.
Does that help explain some more why this can really steam some people? And why there are websites, like Flickr, that say you have to use active codes to post pictures that you've put on their bandwidth in other places? Essentially they don't mind you posting Flickr pictures elsewhere, if the person looking at the picture can click on the picture and be brought to the Flickr website of origin.
Hopefully I have not managed to confuse you!