I've tried to give a gentle definition of the term, without sounding condescending to those who know about the command line already. I've also tried to provide helpful links.
Have I done it right? Are you happy with what I've come up with, or am i going in the wrong direction altogether?
Aside from this: I think the Excerpt might be a bit too basic. I'd be thankful if somebody has a better idea for what to put in it. As I've said, this tag is important to me.