This cable can be used with Raspberry Pi 4 with USB-C power connector and capable of carrying ~3A current. You can use a USB power supply rated 5-5.1V and 2.5-3A with this cable.
If you have been working with a Raspberry Pi long enough, you'll realize one annoying thing - the Pi doesn't have a power switch. You'll know how troublesome it is to power it on and off especially during setups, installations or GPIO wiring. The common way of doing it is reaching out to the wall socket and flick the power switch or if you feel lazy, just pulling out the USB cable from the Pi. Soon, you'll be worry about the connector getting loose or even worse, damaging the connector, given the flimsy nature of the USB plug.
This is not your regular USB A to USB-C cable. It has a push button switch near the USB-C end. Push once to power it on, push once more to turn if off....easy peasy! It adds a little convenience to your life.
This cable can also be used to power other devices that has USB-C power port or to charge your mobile devices. However, it doesn't carry data, therefore you can't use it as a sync/data cable.
