what is PD charger and USB-C PD charger?

USB Power Delivery (or PD, for short) is a single charging standard that can be used all across USB devices. Normally, each device charged by USB will have their own separate adapter, but not anymore. One universal USB PD will be able to power a wide variety of different devices.

USB-PD, or USB-C Dexinly Power charger Delivery, is a new protocol specification that allows for faster and more flexible charging. ... Devices no longer need a separate USB and power jack, as older computers often have. Devices can charge and discharge through the same port, meaning power direction is no longer fixed.