Computers have been revolutionizing industries for the past few decades. With advancements in technology, computers have enabled humankind to solve very complex problems with very innovative ideas.
Quantum Mechanics is a field of study (in physics) that describes nature at the smallest – including atomic and subatomic – scales. QM has evolved into a field of study with early scientific observations/inquiry since 17th and 18th centuries.
Some prominent scientific theories within quantum mechanics are intriguing reads as one starts to understand the subject
Excerpts from the wikipedia page on Quantum mechanics applications
Quantum mechanics has had enormous success in explaining many of the features of our universe and is often the only theory that can reveal the individual behaviors of the subatomic particles that make up all forms of matter (electrons, protons, neutrons, photons, and others). Quantum mechanics has strongly influenced string theories, candidates for a Theory of Everything.
In many aspects modern technology operates at a scale where quantum effects are significant. Important applications of quantum theory include quantum chemistry, quantum optics, quantum computing, superconducting magnets, light-emitting diodes, the optical amplifier and the laser, the transistor and semiconductors such as the microprocessor, medical and research imaging such as magnetic resonance imaging and electron microscopy. Explanations for many biological and physical phenomena are rooted in the nature of the chemical bond, most notably the macro-molecule DNA.
A more interesting and fascinating read is the Many-worlds interpretation
OK so what is quantum computing then?
It is simply the use of quantum-mechanical phenomena such as superposition and entanglement to perform computation. A quantum computer is used to perform computation, which can be implemented theoretically or physically. There are two main approaches to physically implementing a quantum computer currently, analog and digital. Digital quantum computers use quantum logic gates to do computation. Both approaches use quantum bits or qubits.
A quantum computer is able to solve problems that would take a fast classical computer billions of years to perform. They’ll enable the simulation of complex quantum systems such as biological molecules, or offer a way to factor incredibly large numbers, thereby breaking long-standing forms of encryption. 1
Quantum Supremacy - The threshold where quantum computers cross from being interesting research projects to doing things that no classical computer can do.
Why is Quantum Supremacy important?
Achieving quantum supremacy would be a watershed moment in the history of computing. At the most basic level, it could lead to quantum computers that are, in fact, useful for certain practical problems.
you can read more significant apprehensions here