Is Nano proof-of-work?

Is Nano really utilizing a proof-of-work consensus mechanism? I've heard that it claims to be lightweight and efficient, but proof-of-work is often associated with energy-intensive mining processes. Could you clarify how Nano's consensus mechanism works and if it truly differs from traditional proof-of-work systems? Additionally, what are the potential benefits and drawbacks of Nano's approach in comparison to other consensus mechanisms?