What is really the function of programming languages?
So, as a beginner, there seems to be 2 answers to your question:
1. programming languages are used to tell a computer how to react. so, for a robotic factory arm, a program tells the arm to move to point A, grab part 1, move to point B, and place part 1 in part 2. Any action that a computer does is controlled by a program, written in a programming language.
2. is the question of why use a programming language? Its like if you wanted a chinese speaker to give you something, but dont speak chinese. Theres a guy that speaks chinese and spanish, but you don't speak spanish. Theres another guy that speaks spanish and English. So you have your request (what you want done), you tell the spanish-english guy and he translates it to spanish (like writing a program in Python), he tells the spanish-chinese guy who translates it into chinese (like compiling a Python program into the 1s and 0s of binary), he tells the chinese speaker who gives you the item (like running the binary code through the processor).
try going to the code playground and see what people are making with all these languages :)
they all have their own strong area, whether it be website development (html/js), game dev (java, c#), or database (sql).
theres a lot of them because some task cant be completed by others (or not as easily)
but i think to truly understand the purpose and usefulness of any language you have to know the language at least a bit