Want to know more about the debt ceiling? This great video from C.G.P. Grey explains it in less than four minutes:
(This is the same guy, by the way, who did the video explaining the difference between the United Kingdom, Great Britain and England.)
Note that the video above makes a lot of points that President Obama has been making -- specifically, that Congress is responsible for its own budget and that extending the debt limit represents paying for bills that have already been racked up, rather than paving the way for more spending.
Republicans would argue that Obama and Senate Democrats haven't been willing to pursue a new budget -- one that would rein in the debt -- which leaves them to fight for spending cuts in other ways, including by using the debt ceiling.
But regardless, the video is well worth the watch.