From Fedora Project Wiki

Fedora 21 Alpha Release Announcement

The Fedora 21 alpha release has arrived, with a preview of the latest free and open source technology under development. Take a peek inside!

http://fedoraproject.org/get-prerelease

What is the Alpha Release?

The Alpha release contains all the exciting features of Fedora 21's products in a form that anyone can help test. This testing, guided by the Fedora QA team, helps us target and identify bugs. When these bugs are fixed, we make a Beta release available. A Beta release is code-complete and bears a very strong resemblance to the third and final release. The final release of Fedora 21 is expected in November.

We need your help to make Fedora 21 the best release yet, so please take some time to download and try out the Alpha and make sure the things that are important to you are working. If you find a bug, please report it – every bug you uncover is a chance to improve the experience for millions of Fedora users worldwide. Together, we can make Fedora a rock-solid distribution. We have a culture of coordinating new features and pushing fixes upstream as much as feasible and your feedback will help improve not only Fedora but Linux and free software on the whole. (See the end of this announcement for more information on how to help.)

Fedora.Next and Fedora 21 Products

Fedora 21 Base

Fedora 21 Cloud

Fedora 21 Server

Fedora 21 Workgroup

Known Issues

Testing and Reporting Problems

Release Schedule