What do the following lines from the Gettysburg Address mean?

34.
It is for us the living, rather, to be dedicated here to the unfinished work which they who fought here have thus far so nobly advanced.
Those of us who are still alive need to promise to continue to fight for the ideas for which these men died.
Those of us who are still alive need to finish the work of burying the dead.
Those of us who are living need to stop fighting immediately.
Those of us who are living must fight harder to finish the battle of Gettysburg so that these men will not have died in vain.

The correct answer is: Those of us who are still alive need to promise to continue to fight for the ideas for which these men died.