TeX is a typesetting system, where the output is defined by command-sequences. Note that https://tex.stackexchange.com is specifically dedicated to TeX questions.
TeX is a typesetting system, where the output is defined by command sequences. It was designed and mostly written by Donald Knuth. TeX was designed with two main goals in mind: to allow anyone to produce high-quality books using minimal effort, and to provide a system that would give exactly the same results on all computers, at any point in time.
There is a Stack Exchange site dedicated to TeX, which is a good place to ask any TeX-related questions.