Recent Chromium build extended the synchronization feature to settings and autofill data. When you setup Chrome sync, you have to option to only synchronize bookmarks, settings or autofill data. Google stores your data online and links it to a Google account. The nice thing about Chrome Sync and other similar services (Opera Link, Mozilla Weave, Google Toolbar) is that you can use any computer and keep your browser's data in sync. Mozilla Weave synchronizes more data: passwords, sessions, browser history, but it's likely that Google will add these features to Chrome. Google could also synchronize extensions and themes.