What is nethack?

Nethack is quite simply the best video game ever made. Seriously.

What is nethax?

Nethax is an ajax implementation of said best video game ever made. It was created to help introduce the game to the legions of children who have no idea what a "shell account" is. The creator also hopes it will allow him to play the game from work.

What are all these symobls on the screen? How do I do anything? What's going on here?

That's the game. You can check out the official guidebook for more information. There are also a lot of exellent sites out there:
nethack.org Officail nethack site.
Wikihack Nethack wiki, filled with useful information.
Alt.org Great online Nethack community where you can play over telnet.

Why are you so fond of this game?

Part of the reason is nostalgia, I figure discovering Nethack my freshman year of college cost me at least a quarter of a point of GPA. Part of it is that it really is a very, very good game and almost totally unlike what's being published these days. If you look beyond the simple graphics you'll find a rich game filled with surprises and nearly limitless variation.

I died and can't reload my game. Why not?

Those are the brakes kid. Nethack doesn't just slap you with a 10% durability reduction when you die. Death really means something here, it means you get to start over again with a level 1 character. Looks like you should have wished for that amulet of life saving.