a set of macros written in 1983 by Leslie Lamport starting from the TeX program; the latter one has been created by Donald Erwin Knuth in 1977 and is "intended for the creation of beautiful books – and especially for books that contain a lot of mathematics".
LaTeX has many advantages if compared to the traditional word processors; it allows to easily set the logical partitioning of the documents in chapters and sections, to manage the bibliography in a very effective way and to reach high quality typographical results, since TeX is built on a very powerful programming language which makes easier to cope with the complex calculations that express the relations between the entities of a text.
When we read a document, we do not usually know that a very good typographic result (and, consequently, a very good readability) is based on the characters good proportions; TeX can be used to achieve it and LaTeX can be thought as a more practical variant for people who type the documents.
We have dealt with several kinds of requests in our past work experience, going from the researcher who submits a draft to us for it to be adapted to publishers' typographical requests to the company which asks us to develop classes for conversion of XML sources of articles to PDF final versions.
Another important task has been to develop LaTeX financial and business brochures to be filled by the customer with data taken from SQL databases and then managed using PHP; the work we have made consisted of a typesetting step (involving fonts and colors appearance, building of graphs and tables) followed by building a variables namespace to facilitate the PHP programmers' work.
Once again, we want to underline that all these tasks have been performed exclusively using open source software; this implies that no additional software costs are charged to our clients.