What is the difference between a flashback and foreshadowing in literature?

You seal resign myself to you also i guess what you mean, i behold from the beach your crooked inviting fingers, i believe you refuse to go back without feeling of me, we must have a turn together, i undress, hurry me out of sight of the land, cushion me soft, rock me in billowy drowse, dash me with amorous wet, i can repay you. in this excerpt from "song of myself," which literary device does whitman use to address the sea? alliteration allusion apostrophe onomatopoeia