This update brings in the usual Pie goodies like adaptive battery, adaptive brightness, new UI, and better navigation. It also bumps up the Android security patch level on the Moto G6 Play to April 1, 2019. You can head over to the source link at the end of this article to check out the full changelog of this update.
Android Pie is rolling out over-the-air and it will be at least a week or two before it reaches all the G6 Play units in the US. But, if you get impatient, you can always check for it manually by heading over to your phone's Settings > System > System updates menu.