This release does not have a Play Store Description, so we grabbed one from version 62.0:

Help refine and polish the newest features almost ready for prime time. With Firefox Beta, you get to test the latest performance, customization and security enhancements before they make it to our next version.
Have an impact by helping to put the finishing touches on features and functionality.
**We need your help testing Intel x86 Atom based devices! If you have an Intel x86 Atom based device, download Firefox Beta and tell us what you think.**

Find a bug? Report it at mzl.la/android_bugs.

Want to know more about the permissions Firefox requests? mzl.la/Permissions
See our list of supported devices and latest minimum system requirements at www.mozilla.org/en-US/firefox/mobile/platforms/.

ABOUT MOZILLA

Mozilla is a proudly non-profit organization dedicated to keeping the power of the Web in people's hands.
We're a global community of users, contributors and developers working to innovate on your behalf.
When you use Firefox, you become a part of that community, helping us build a brighter future for the Web.
Learn more at www.mozilla.org.