"Because we spend so much time online, we began seriously thinking about what kind of browser could exist if we started from scratch and built on the best elements out there. We realized that the web had evolved from mainly simple text pages to rich, interactive applications and that we needed to completely rethink the browser. What we really needed was not just a browser, but also a modern platform for web pages and applications, and that's what we set out to build."

Here's a comic book that explains Google Chrome.

Some have asked if Google Chrome will impact Google's (financial) support for Firefox.  Google's search-related payments to Mozilla make up a significant portion of Mozilla's revenue.  Google is deflecting these questions by playing the choice card:

"The web gets better with more options and innovation. Google Chrome is another option, and we hope it contributes to making the web even better."

On the open source front, Google announced that they are using components from Firefox and Apple's WebKit.  Since Chrome is also open source licensed (not sure what license), they hope Apple & Mozilla et al. will build upon ideas from Google Chrome.