In informatics theory I hear and read about high-level and low-level languages all time.
Yet I don't understand why this is still relevant as there aren't any (relevant) low-level languages except assembler in use today.
So you get:
Low-level
Definitely not low-level
High-level
And if assembler is low-level, how could you put for example C into the same list. I mean: C is extremely high-level compared to assembler. Same even for COBOL, Fortran, etc.
According to Wikipedia, the low level languages are machine code and assembly.
From the source:
In computer science, a low-level programming language is a programming language that provides little or no abstraction from a computer's instruction set architecture. The word "low" refers to the small or nonexistent amount of abstraction between the language and machine language; because of this, low-level languages are sometimes described as being "close to the hardware."
Then, to answer:
So why does everybody keep mentioning high and low-level languages if assembler is really the only low-level language.
I don't know who "everyone" is, but I would venture a guess that back when high-level languages were not as commonplace as they are today, it was more relevant to talk about low-level vs. high-level (because there was a relatively significant amount of programmers writing assembly code). In modern times it is a less important distinction. Personally, I rarely hear people using these terms except to differentiate between assembly or not (except for those times when you might hear someone raised on Python referring to C or C++ as low-level, but this is not in the spirit of the original definition).