The word “LaTeX” actually consists of two components, “La” and “TeX”. In the following we will briefly describe where they come from.
TeX was originally invented by Stanford professor Donald Knuth. Knuth is well known for a series of books called “The Art of Computer Programming” (known as “TAOCP”). In 1973 a new edition of the books was to be made; this was the time when the typesetting industry switched from traditional typesetting with lead to photo-based typesetting. Donald Knuth did not like the quality of the print and therefore decided to implement his own typesetting system.
In May 1977 the development of TeX started.
The original TeX was rather complicated to use, even Donald Knuth used various macros to edit his books. Leslie Lamport, who works for Microsoft nowadays, also developed a set of macros that simplify the use of TeX and called this macro set “LaTeX”.
Today LaTeX is the most common way to interact with TeX. Another alternative is ConTeXt.