What are programming languages?

So we got an algorithm or process we pretend to program. What is next? We have to write it in such a way that the hardware understands it (so it can run it!). Here we have a problem: the human-language is not understandable by machines (not by themselves). We need some kind of an interface between the machine and us: a programming language. In the background, programs are always translated to machine code. Such translation is done an auxiliary program.

There are many programming languages out there: Java, C, Pascal, Fortran, Octave, and so on. However, only few of them are popular (used frequently). However, the popularity of each programming language changes with time. Good news are that, once you learn one of them, learning another becomes easier; the third one even easier, and etcetera. They all follow certain patterns: they all have a way to handle variables, for example.

The 10 most popular programming languages in 2015, by IEEE Spectrum.

But why don't we program in machine-language directly? The problem with the machine language is that it is so hard to read and write by humans that it becomes unpractical for coding. Most hardware systems only understand specific combinations of ones and zeroes (binary code), and that is what machine language is. Moreover, the machine language changes with the processor model. Then a program that has been written in machine-language may not work on different machines!

Some programs are easier to translate to machine-code, and therefore, they are harder to understand by humans. Such languages are called "low-level" programming languages. On the other hand we have "high-level" languages, that are easy to understand by humans, but more difficult to translate to machine code.

Programs written in low-level languages tend to run faster than programs written in high-level languages. However, high-level programs tend to run independently of what hardware executes it, while the low level programs should be re-translated or re-coded to run on different machines. But at the end, choosing a programming language or another depends on the application and how it gets impacted by the language characteristics.