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This is an entry for the STEM contest being run by stemgeeks and @themarkymark. You can join the STEM contest fun here!

Our current understanding of reality is dominated by the twin giants of Quantum Mechanics and General Relativity which were born from a deeper understanding of Physics that began when early 20th century (and late 19th century) scientists began understanding that the Newtonian description of the Universe was starting to show it's limitations by producing incorrect predictions that did not line up with observations.

Of course, this didn't immediately invalidate Newtonian physics with its vast array of correct predictions (that's not the way Science works...)... however, it did start to put bounds upon the validity of application of what now appeared to be an approximation of a larger theory. Or in this case, two separate strands of theory that would later come to be known broadly as Quantum Mechanics and General Relativity.

The Problem

Event Horizon Telescope press release

In more recent (last half century or so...) times, it has become apparent that Quantum Mechanics and General Relativity are perhaps further approximations of a deeper understanding of how the Universe works. In their realms of applicability (Quantum Mechanics on small scales and General Relativity on large scales), both theories have been wildly successful in their predictions and resolving the problems of Newtonian physics. Despite portraying a reality that is far removed from our everyday "common sense" experience, they have proved time and again to be true and accurate depictions of the our Universe.... in fact, they are the underlying theories behind much of our modern technology (take that, anyone who thinks abstract and non-practical research should be defunded in preference for research that makes immediate money....).

However, in situations where their realms of applicability overlap, there is a large discord between the two pillars of our Physics. They just fundamentally disagree with each other... which leads us to the conclusion that one or the other (or more likely, both) is at best an approximation of a larger theory which we have not yet glimpsed. One such realm is in the local vicinity of a black hole, where the gravity (space-time curvature) is described by General Relativity but occurs on distance scales that are governed by Quantum Mechanics.

On a more fundamental level, the way that they describe the universe is also quite different. Quantum Mechanics sees the universe being made of fundamental steps (quanta) in properties, with time and space being fundamental properties of the Universe. General Relativity is a smoother and continuous depiction of the Universe, with space and time being more like emergent properties.

This is a problem that has baffled Physicists for over half a century... however, the disagreement between the two theories has been ignored, as it has been possible to keep the theories operating in their different and non-overlapping realms of applicability. This has allowed Physics to further refine both theories and harness them to produce practical technology. However, it is an impasse that will need to bridged to gain a better understanding of reality.

A Unified Theory is a theory that would supersede both theories, with both theories falling out as special conditions of the overarching theory. The approaches to developing a Unified Theory has started with one theory (Quantum or Relativity) as a basic starting point and then trying to incorporate the other into the same language and physical outlook. The leading contender in this space has been String Theory. However, despite some progress having been achieved, the end goal still remains elusive.

Conclusion

With new detection instruments (and their relevant data) coming online... it is possible to probe the Universe for more clues into this elusive theory. It is possible that humanity is on the cusp (although... we have been on the cusp for a while...) of discovering a better way of describing the Universe.

Why would this be important? Well... if you ask me (someone who studied Physics with an emphasis on the Theoretical and Mathematical), I would say... what, why not? If there is a better and deeper way to understand something... well, you should! A Deeper understanding on this level could resolve ideas about what time and space really are, make better predictions about how black holes (and their local area) behave and just a deeper and more refined understanding... really, I should just write that over and over... deeper understanding, never bad... always good!

However, I realise that there are some need less abstract motives and more "grounded" reasons... so, understanding something means that you can better harness your knowledge to develop things that can get you your 30 pieces of silver.

PS: Again, much of this is simplified for easy layperson reading... don't flame me!