Out-of-control Russian rocket falling to Earth

A large Russian rocket, the Angara A5, experienced a failure during its third test flight. The rocket's third stage failed to fire a second time, leaving it and its dummy payload stranded in low Earth orbit. This malfunction prevents the rocket from reaching its intended graveyard orbit. Experts predict that the 20-ton structure will begin falling back to Earth, with most of it burning up in the atmosphere, but some parts may impact the surface.

What is a graveyard orbit, and why is it significant in this context?

When is it predicted that the structure will start falling out of the sky?