The Chromium blog team explained a little bit how the sandbox in Google Chrome protects you when browsing. As a note, Google Chrome is the web browser that Google released, while Chromium the open source project from which Google Chrome is compiled.
As for the explanation of the sandbox:
Chromium helps protect your computer from malware by running some parts of the browser in a sandbox. The sandbox tries to limit what an attacker can do after exploiting a bug. In particular, the sandbox aims to prevent malicious web sites from automatically installing software on your computer and from reading confidential files on your hard drive.
[...] The sandbox doesn't prevent every kind of attack (for example, it doesn't stop phishing or cross-site scripting), but it should make it harder for attackers to get to your files.
The full post can be read here. This kind of "each tab as a process in a sandbox" implementation resembles less with a browser, and more to an operating system - what many other people think that Google is going to transform Chrome into.
