Oxide Interactive

MathML is a markup language used to facilitate the sharing of mathematical equations on the web. It contains both presentational and structural elements, allowing you to show how the equation looks, but also how it actually works.

A carefully encoded MathML expression can be evaluated in a computer algebra system, rendered in a Web browser, edited in your word processor, and printed on your laser printer. Source

Like many web technologies, actually achieving this optimistic description in the real world is not straightforward - some care must be taken when placing MathML equations in your HTML pages.