It is a large set of macros built on top of TeX, a digital typesetting language created by Donald Knuth at Stanford in the 1970s. LaTeX was originally written in 1984 by Leslie Lamport and has become the dominant method for using TeX—few people write in plain TeX anymore. A more recent version, called LaTeX 2e, is an outgrowth of the LaTeX3 project led by Frank Mittelbach. AMS-LaTeX, a set of LaTeX enhancements by the American Mathematical Society, provides enhanced mathematical typesetting capabilities, three new LaTeX 2e document classes, scores of new math symbols, and four new math alphabets. Articles written with AMS-LaTeX are of the same high quality as those found in the journals of the AMS. LaTeX offers programmable desktop publishing features and extensive facilities for automating most aspects of typesetting and desktop publishing, including numbering and cross-referencing, tables and figures, page layout, bibliographies, and much more.
LaTeX is based on the idea that authors should be able to focus on the meaning of what they are writing, without being distracted by the visual presentation of the information. In preparing a LaTeX document, the author specifies the logical structure using familiar concepts such as chapter, section, table, figure, etc., and lets the LaTeX system worry about the presentation of these structures. It therefore encourages the separation of layout from content, while still allowing manual typesetting adjustments where needed. This approach is often regarded as superior to that of "WYSIWYG" word processors and most desktop publishing (DTP) systems, which make isolated visual layout changes easy, but tend to intertwine content and form so tightly that maintaining overall consistency in a document is often difficult. Conversely, purely structural systems such as SGML and XML do not directly address presentation at all, relying instead on separate "style" languages such as CSS to handle visual formatting. LaTeX provides great flexibility in both areas.
LaTeX can be arbitrarily extended by using the underlying macro language to develop custom formats. Such macros are often collected into packages which are available to address special formatting issues such as complicated mathematical content or graphics. In addition, there are numerous commercial implementations of the entire TeX system, including LaTeX, to which vendors may add extra features like additional typefaces and telephone support. LyX is a free visual document processor that uses LaTeX for a back-end. TeXmacs is a free, WYSIWYG editor with similar functionalities as LaTeX, but a different typesetting engine.
A number of popular commercial DTP systems use modified versions of the original TeX typesetting engine. The recent rise in popularity of XML systems and the demand for large-scale batch production of publication-quality typesetting from such sources has seen a steady increase in the use of LaTeX.