Gears, formerly Google Gears,is software offered by Google that “enables more powerful web applications, by adding new features to your web browser. It allows some online files to be used offline” Released under the BSD license, Gears is free and open source software.
Offline Gmail is available in the UK and USA today, but you’ll need Gears to run it! Of course Gears has a number of other uses too. Gears is a plug-in that extends your browser to create a richer platform for web applications. For example, webmasters can use Gears on their websites to let users access information offline or provide you with content based on your geographical location. Gears was designed to be used on both Google and non-Google sites. A number of web applications currently make use of Gears, including two Google products: Google Reader and Google Docs (and now Gmail !) . Additionally, Zoho and Remember the Milk have been using Gears since its original launch. If you’re running Windows Mobile on your cellphone, Picasa Web Albums also makes use of Gears. Gears works with a select group of sites that are specifically designed for compatibility. When you visit a site that’s configured to work with Gears, you should see a message stating ‘The website below wants to use Gears.’ If you’d like to allow the use of Gears on this site, simply check the box next to ‘I trust this site. Allow it to use Gears.’ and click the Allow button. To use Gears, you’ll need one of the following:

• Microsoft Windows XP or Vista with Firefox 1.5+ or Internet Explorer 6+
• Apple Mac OS X 10.4+ with Firefox 1.5+
• Apple Mac OS X 10.4.11 (or higher) or 10.5.3 (or higher) with Safari 3.1.1
• Linux with Firefox 1.5+
• Microsoft Windows Mobile 5 or higher, with Internet Explorer 4.01+