How do you explain M2?

Excuse me, could you elaborate on what M2 represents in the context of economics and finance? I'm a bit unfamiliar with the term and I'd like to have a clearer understanding of its significance. Specifically, how does M2 differ from other monetary aggregates like M1, and what factors influence its growth or decline? Additionally, how does M2 play a role in determining the overall health of an economy and its implications for monetary policy decisions?