From the introduction:
This document is the third in a series of Unearthed Arcana articles that present material designed for the next version of the Player’s Handbook. The material here uses the rules in the 2014 Player’s Handbook, except where noted. Providing feedback on this document is one way you can help shape the next generation of D&D! Inside you’ll find the following content:
Cleric Class. The Cleric Class is available for playtesting, along with one Subclass: the Life Domain. More Subclasses will appear in Unearthed Arcana in the months ahead.
Revised Species. Three revised Species appear in this document: the Ardling, the Dragonborn, and the Goliath.
Rules Glossary. In this document, any term in the body text that is underlined appears in the glossary at the end. The glossary defines game terms that have been clarified or redefined for this playtest or that don’t appear in the 2014 Player’s Handbook. This rules glossary supersedes the glossary in previous Unearthed Arcana articles.