Dry form of hydrogen peroxide. Uncoated In laundry, Sodium Percarbonate is used to destain, deodorize, and whiten. It is very effective as a laundry presoak for heavily stained articles.
It is a granulated powder – which can be nice for scrubbing stains and stuck-on-gunk off of dishes. Think of scouring powder, but made out of hydrogen peroxide. It can be made into a paste, too, and used on tile grout and tough stains.
It is easy to carry around -- say, to a laundromat – because of its dry powder form. In fact, laundry products are one of the big applications of sodium percarbonate.
The usual cautions for hydrogen peroxide also apply to sodium percarbonate: check for colourfastness, keep it out of eyes.
After you mix it in water, the label cautions that you must not seal the container. The sodium percarbonate will continue to break down rapidly and release oxygen, and the container could burst!
It is recommended to mix it into HOT water. I tried mixing some into cold water, and it does work to mix into cold water, so it is not required that you use hot water -- but it mixes more easily into hot water.
It is not regulated for use for food preparation or on skin (etc), so I don’t know how “clean” it is. I would be reluctant to use it in my bath, for example.
It takes some time to completely dissolve. If you're in a hurry, liquid peroxide is faster, since it doesn't need to "break down" into peroxide (it already is peroxide). Sodium percarbonate needs to break down to turn into peroxide (and soda ash).