Texmaker is an editor for the document markup language LaTeX. It lets you concentrate on the content of a document, while the underlying LaTeX engine takes care of the layout. Whether you are experienced with LaTeX or just starting out, Texmaker makes LaTeX easier to tame. It is GPL-licensed, cross-platform (running on Linux, Unix, Windows, and Mac OS X), and extremely stable.
It's a common misconception that LaTeX is useful only for people who write documents with extensive mathematical formulas. It's true that LaTeX stands out when it comes to making professional-looking mathematical formulas, but it's far from the only thing LaTeX is good at. People in the academic world can also benefit from its citation and footnote facilities. Even for people writing non-scientific documents, Texmaker is a great tool. The fact that Texmaker helps you focus on the content without distracting you with typography, is something every writer will benefit from, especially when working with long, highly structured documents such as articles, reports, and books.