For more and more people mobile devices are the primary way, or even the only way, to access the Web. Firefox for Android (codenamed Fennec) is an open, hackable, standards-based browser, just like the desktop Firefox.
Firefox for Android constructs its user interface from native Android widgets instead of XUL: this greatly improves performance, especially startup time, and memory consumption.
The main starting point for information about the Firefox for Android project itself is the project "Get Involved" page.
You can help us to create and improve Firefox for Android:
We've started putting together a guide to designing web sites for mobile devices.
With Firefox for Android, you've got access a number of APIs that expose the underlying capabilities of the device, closing the gap between the Web and native applications:
Firefox for Android supports add-ons using the same WebExtensions system as desktop Firefox.
Documentation and tutorials for using and troubleshooting Firefox for Android are available on the Mozilla Support website.
If you don't already have Firefox installed on your Android device, you can do so at the Google Play store. See the SUMO article Install Firefox on an Android device using Google Play for detailed instructions.
There are some unofficial builds and specialized installations for devices which don't officially support Firefox for Android. Here are some helpful links for these (keep in mind they are not supported by Mozilla and you are using them at your own risk!).