Copper is one of the abundant elements in the Earth's crust. Copper is also one of the most versatile and useful elements.
Humanity has used copper during thousands of years very lavishly. Naturally during the past century copper has been extremely useful and used because of its electrical properties: It's a very good conductor of electricity and heat. As a conductor it's one of the best materials for all kinds of electricity transportation, as it incurs relatively low losses (unlike, for example, iron, which also has good conductivity, but incurs significantly higher losses when conducting electricity.) For this reason copper is the main material used for electrical wires, and all other sorts of electric conductors. (Copper is not the absolutely best material for this purpose, but its advantage is that it's cheap. There are better conductors, like silver and gold, but those are significantly more expensive.)
However, copper is not used solely on electric wires and circuits. It has been used (and is still being used) very lavishly in all kinds of construction. Millions of tons of copper have been used for things like pipes, roofs, statues and the like.
The use of copper has only increased in the modern era. 95% of all the copper ever mined in the history of humanity has been mined in the last century. Over half of that has been mined in the last 25 years.
This has, in fact, become a problem. While the amount of copper in the Earth's crust is extremely vast, only a minuscule portion of it is actually directly usable (the majority of it appearing in compound elements, where it's very hard to extract from.) And we are, in fact, running out of mineable copper. While a hundred years ago copper could be mined almost anywhere, nowadays copper mines need to become deeper and deeper. Almost all of the copper that's easily retrievable near the surface has been mined.
There is, obviously, a limit to how deep we can dig, and how easily we can find usable copper. And the demand and use for copper is not decreasing, but the exact opposite. We are needing to mine more and more of it each year, at an increasing rate, due to demand. And we are running out of places where to mine.
We are, in fact, running out of copper sooner or later. Most estimates say that we will run out of it in less than a hundred years from now (the most pessimist estimates a lot less than that.)
This is yet another thing where humanity will face a crisis in less than a hundred years. Once we run out of copper from mining, we are pretty much screwed. (Humanity will probably start recycling copper, but that's probably not going to be enough, without some serious cutbacks.) Unless we can figure out a more abundant alternative for copper, we are screwed.