what does a webmaster do?

I am currently a Web Manager. This position is probably best described as a Webmaster, and is a very varied, and demanding job. However, this variety makes the job of a Webmaster a very interesting one.

A Webmaster will deal with everything in running a website, from the design and development of the website, to its maintenance and marketing.

There are a number of resources which give further information, such as the Wikipedia page, and also this article: What does a Webmaster do?.