Blunt ends are double-stranded DNA molecules that have no overhangs at their ends, whereas sticky ends are double-stranded DNA molecules that have single-stranded overhangs at their ends. Blunt ends can be used for cloning, restriction digestion, and DNA ligation, while sticky ends can be used for DNA ligation, recombinant cloning, and DNA sequencing. Blunt ends are ideal for creating a double-stranded DNA molecule with a known sequence, while sticky ends are ideal for creating a double-stranded DNA molecule with an unknown sequence.