LaTeX is a high-quality document preparation system and document markup language which was written by Leslie Lamport. It is a very mature system and has been in development for more than 20 years. It includes features designed for the production of technical and scientific documentation.
An easy way to get started in LaTeX is to study online books and web sites. This article highlights 14 free LaTeX books, some are short general introductions that offer a gentle learning curve, other books show you how to fully exploit the preparation system.