We spend more than we take in.. it's gotta give sometime. That's why you stock on guns, ammo, food, water, tools.
It was a term coined by Bernanke for a bunch of automatic spending cuts and tax increases that we imposed on ourselves if we didn't have our budget deficit problem under control by January 2013. It's a big deal because if we don't do anything (like raise the debt ceiling or extend some of the Bush tax cuts) it'll send us back into recession.
Well you see, the term is a scare tactic. If anything we went over it four years ago. Basically, if we don't do anything, everyone's taxes will go up.