Lincoln had at least two audiences when he delivered his speech at the dedication of the Gettysburg National Cemetery on November 19th, 1863: the immediate audience who stood in front of him on that day and the larger American public.
As he stood before the audience on that Thursday in 1863, Lincoln was called to speak to the losses of the Union soldiers. Local townspeople, politicians, journalists, and soldiers gathered together that day to commemorate the use of this land for solemn purposes. Undoubtedly, some of those in the audience were surviving family members of those who had recently been killed in the battle with Confederate troops. Lincoln made great efforts to console and encourage these people to continue the noble fight, despite their losses, because of a great purpose:
We have come to dedicate a portion of that field, as a final resting place for those who here gave their lives that that nation might live.
These soldiers died so that an entire "nation might live"—and not the fragmented one which existed during the Civil War. To this end, Lincoln addressed the direct emotional needs of those who stood before him in Gettysburg that day.
Yet Lincoln would have certainly been aware that his words were being transcribed by the journalists in the audience. He was therefore also speaking to the greater American populace, reminding them that there was unfinished work which still required their courageous efforts:
The world will little note, nor long remember what we say here, but it can never forget what they did here. 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.
Lincoln was asking all of the "living" to remain steadfast as they continued the work of these "noble" soldiers. He called upon Americans as a whole to "devote" themselves to "a new birth of freedom" so that the American form of government would not "perish from the earth."