What is Armistice and when did it happen?

The Armistice was  the ceasefire that ended hostilities between the Allies and Germany on the 11th of November 1918. 

From the earliest starting point of the war, an objective of the Union armed force was to catch the Confederate capital at Richmond. Petersburg had been the last barrier in Grant's way. Following a nine-month attack, Grant at long last drove Lee's armed force out of that city. Jefferson Davis realized that Richmond was devastated.