Firefox is a web browser and a good one too, with a lot of extensions some of which are actually useful. I think adblock+ is the most useful for most people.
The web part of the internet is always evolving and as it evolves browsers are rewritten to take advantage of it. As web browsers are complex there are always problems that are discovered and fixed. Firefox is updated regularly.
It's a good browser but there are others Google's Chrome browser for example has speech input built in. As browsers are built to support open standards which one you use is pretty much personal preference.
Firefox is my personal favourite and is easy to avoid getting loaded up with toolbars which sometimes give you a view of a webpage similar to looking through a letterbox.