V8, the Javascript engine of the new Google Chrome web browser, is Big News. Sort of.
The web is written, for the most part, in three computer languages: HTML and CSS for the structure and presentation, and JavaScript (or ECMAScript) for all that fancy stuff. (Plus some Flash for things like YouTube videos.) GMail, Google Documents, Google Maps, E2's WYSIWYG writeup editor, and countless minor effects on many websites are written in JavaScript. (Try disabling JavaScript sometime--or, better yet, install the Firefox extension NoScript--and you'll see just how prevalent JS really is. Half the websites will have broken features or will become completely unusable.)
But JavaScript is an interpreted language, and consequently is about 1-10% as fast as a compiled language. If you're just making a single pop-up alert, that's no big deal, but when you get into JavaScript application like GMail, it starts to be noticeable. Programs on your computer are usually written using compiled languages, so it's hard to compete on the web. Google is big on competing on the web using JavaScript applications, so they made V8, which actually compiles the JavaScript*, boosting its performance up to compiled language speed.
As a result, Google Chrome has JavaScript performance that beats Firefox, Opera, and Safari by a ridiculous margin. This is Big News, especially for us JavaScript hacks who suddenly realised that we really need to learn a rich JavaScript library so we can start building full JavaScript applications. It's, of course, also Big News for everyone else because now this ever-expanding supply of (usually free) online applications will be faster and more powerful.
On the other hand, it's also not so big news, because while, yes, V8 is the first to put this out there, other JavaScript engines are already in the works at Firefox (TraceMonkey, which will be included in Firefox 3.1 next year), and Apple (Safari's SquirrelFish Extreme). (What are the guys from Opera doing, you ask? Being secretive, I guess, 'cause I sure can't find anything from them.)
It would be a mistake, one would presume, to credit Google/V8 with prompting this new, faster model, as the Firefox people started work on their upgrade long before V8 was announced to the public. But they got it out the door first, and that counts for something.
You can download Google Chrome, which uses V8, from http://www.google.com/chrome
* Initially I described V8 as a Just In Time compiler, mislead by several evil online sources. nyte pointed out my mistake. Various sources agree with him, and I'm inclined to believe them--and him.