USB-C Power Delivery, often called USB PD, is a charging standard used with USB-C connectors. It lets a charger, cable, and device communicate before deciding how much power should be sent. This is safer and more flexible than a charger simply pushing one fixed amount of power.
A small device may need only a little power, while a laptop may need much more. With USB PD, the charger can offer several power levels, and the device can request the level it supports. If the cable is also rated for higher power, the system can allow faster charging. If not, it should stay within safer limits.
USB-C describes the connector shape, but it does not automatically mean every cable or charger supports the same speed or power. That is why two USB-C chargers can behave very differently. One may be good for earbuds, another may charge a phone quickly, and a stronger one may run a laptop.
Power Delivery is useful because it reduces the need for many separate chargers. A good USB PD charger can power a phone, tablet, handheld device, or laptop if the wattage and cable are appropriate. It also helps devices negotiate direction, because some products can both receive power and provide power to another device.
The simple rule is to match the charger, cable, and device. USB-C Power Delivery can be fast and convenient, but the weakest part in the chain controls what is actually possible.