Why is supply and demand important to learn?

They are the most fundamental principles of economics and business, supply is the amount of goods that can be sold, and demand is what determines the price of these goods. If a country has too much supply and not enough demand, then price and profits go down and vice versa. This applies to corporations, entire nations, and the global economy as well. If you understand the workings and implications of supply and demand you'll also understand the workings of economies and businesses as well.

It is not important to liberals. They're happy with their Obama and his sick regime dictating what demand shall be.

Without supply, there can be no profits. no profits leads to companies downturn, workers lost, no salaries.
No demand, the money flow stops. The economy has to keep going to provide supplies to households (and firms).
The market price is people are willing to trade at a particular time at a given price, centus paribus, vice versa.

Because it's what determines prices which are the basic data of economics.

they are invisible.

If you do not live self-sufficiently on a desert island, your daily life is governed in some way or other by the "rules" of supply and demand.

For everyday life you do not need to know about that idea in detail, but you need to be aware of its operation for most of mankind - even those living in an extreme socialist system. The comment by "Anonymous" is not helpful.

Because it's the basis for many economic systems, such as capitalism.

...so you don't spend too much on product that sits on the shelf for too long... or otherwise loses value...

It's a pretty technical thing.

You never want to be chronically out of stock, either.

Consumers will lose faith in the store if what they want is never there.

yes