Gears allows web applications to have the same functionality enjoyed by desktop apps. It does this through a browser extension that can be installed for a range of browsers (Firefox, Safari, and Internet Explorer) on a range of operating systems (Windows, Windows Mobile, Mac OS, and Linux). The Google browser, chrome, comes with gears support, which makes it a more powerful browser.
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.