Mathjax enables enables rendering of embedded latex or mathml in HTML pages. This plugin adds this functionality to wordpress. The mathjax javascript is inject on-demand only to those pages which require it. This ensures that mathjax is not loaded for all pages, which will otherwise slow loading down.
The MathJax javascript can be delivered from your own server, or you can utilize the [MathJax Content Distribution Network (CDN)] (http://www.mathjax.org/docs/latest/start.html#mathjax-cdn), which is the preferred mechanism as it offers increased speed and stability over hosting the Javascript and configuring the library yourself. Use of the CDN is governed by these Terms of Service.
You may embed latex using a variety of different syntaxes. The shortcode (http://codex.wordpress.org/Shortcode_API) syntax is preferred. So [latex]E=mc^2[/latex] will work out of the box. This also forces loading of mathjax.
Additionally, you can use native mathjax syntax — $$E=mc^2$$ or (E=mc^2). However, if this is the only syntax used, the plugin must be explicitly told to load mathjax for the current page. This can be achieved by adding a [mathjax] shortcode anywhere in the post. For posts with both [latex]x[/latex] and $$x$$ syntaxes this is unnecessary.
You can use wp-latex syntax, $latex E=mc^2$. Parameters can be specified as with wp-latex but will be ignored. This means that mathjax-latex should be a drop in replacement for wp-latex. Because this conflicts with wp-latex, this behavior is blocked when wp-latex is present, and must be explicitly enabled in the settings.
You can also specify [nomathjax] — this will block mathjax on the current page, regardless of other tags.