Extensions let you personalize Firefox to fit your needs. With extensions, you can change the look and feel of Firefox, enhance existing functionality, and add functions. For example, extensions can enhance the download manager, show the weather, or control Web music players. Other extensions assist Web developers or increase security by blocking content such as ads or scripts.
There are thousands of extensions available for Firefox. With the add-ons manager, you can install, enable, disable, update, and remove extensions.
If you do not like the standard look and feel of Firefox, install a new theme. Themes do not change the functionality, only the appearance of the browser.