During DNA replication, Okazaki fragments are used to elongate

The polymerase molecules responsible for construction of the two new strands of DNA both move in 3’ → 5’ direction along the template, and both construct a chain that grows from 5’→3’ and consequently one of the newly synthesized strands grow towards fork (leading strand) and the other strand grows away from the fork (lagging strand). Therefore, Okazaki fragments are used to elongate lagging strand away from the replication fork.