On the INSERT statement in H2, what does `DIRECT` mean?

I noticed on the grammar documentation for INSERT in the H2 Database Engine , the optional word DIRECT. The documentation says: >When using DIRECT, then the results from the query are directly applied in the target table without any intermediate step. When is data inserted *not* “directly applied”? What are these “intermediated steps”? ➥ What is the purpose of DIRECT? ➥ In what scenarios might one be motivated to use this feature?