What's the matter with Dark Matter?

When we look at the night sky we see a variety of astronomical objects, e.g., planets, stars, gas clouds still waiting to form stars, etc., and swathes of emptiness. For a long time it was believed, this was all that there was in the Universe. It came as a huge surprise that all this stuff we see and know comprises only about 20% of the mass of the Universe. The remaining 80% is invisible, and called "Dark Matter." What is this dark matter? How do we know that it's out there? Is it made of new undiscovered particle? Or is it something else? What are its properties? What are we doing to unmask the identity of this mysterious new entity? In this talk we will address and answer these questions at a super non-technical level.