What does "flotsam and jetsam" mean?

Discarded odds and ends, as in Most of our things have been moved to the new house, but there's still some flotsam and jetsam to sort. [Mid-1800s]

Destitute, homeless individuals, as in The mayor was concerned about the flotsam and jetsam of the inner city. [Second half of 1900s] Both words originated in 17th-century sailing terminology. Flotsam literally meant “wreckage or cargo that remains afloat after a ship has sunk.” Jetsam meant “goods thrown overboard from a ship in danger of sinking in order to give it more buoyancy.” Both literal meanings remain current, although the distinction between them is often forgotten.