What is depicted by the diagram?

The diagram clearly shows that is the process of DNA replication that takes place in S stage of cell cycle. It shows that both strands of DNA acts as template. On a strand of DNA template with 3ʹ → 5ʹ polarity, there is continuous formation of daughter DNA strand known as leading strand. On the other strand of DNA with 5ʹ → 3ʹ polarity there is formation of daughter DNA strand in fragments. The daughter DNA strand is called lagging strand and its fragments as Okazaki fragments.