I am not getting the difference between TeX and LaTeX. I have seen the answer here but I am not getting it completely. Is TeX a system or language or format or program and Is LaTex a system or language or set of macros(what is macro here) or library or engine. If I say, LaTeX is a TeX based-language then what is TeX ? In wiki, it is written that "TeX is a macro and token-based language" and It is a Turing-complete language. So,It means TeX is a language. Now, the 3rd answer here is saying that TeX is an engine which loads the LaTeX format and then process it. It means TeX processes the LaTeX. Since, both TeX and LaTeX are the languages then how is it possible that one language processes the another language ? I am a beginner in this area. Please explain in simple words, "what actually the TeX is" and "what actually the LaTeX is" ?