In the lab we use LaTex (pronounced lay-tech or, alternatively, la as in lava and tech as in technology) for writing papers and general documentation.
LaTeX is a markup language.
The advantages of using a markup language like LaTeX rather than a WYSISYG text editor like MS Word is that your documents are written in plain text, so it is easier to collaborate with others and to manage drafts using version control software like git. LaTeX handles mathematical formulas much better than many word processors and it is platform independent.