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. To install Gears, visit http://gears.google.com
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. 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.
If you're a developer interested in utilizing Gears on your site, visit the Gears developer site for more information.