What is a barrow and why is it significant?

A barrow is a large mound built over gravesites. In the final battle, Beowulf tells his men to wait on the barrow, which they do until the dragon's fierceness frightens them and they run away. Perhaps its significance is metaphoric. The men are waiting on their graves - a symbol for the tribal theory of "sparrow through a mead-hall," that life is short so we should seek greatness. The men are frightened and try to prolong their lives (they rush from the barrow) where Beowulf shows his heroism by fighting to the death.