Ashing is a process that turns solid things, like food or plants, into a type of powder called ash. This is done by heating the solid things up really hot and burning away all the parts that are not ash.
Let's say you have a piece of wood. You can use a special machine called a furnace to heat the wood up until it burns and turns into ash. The machine gets very hot and makes the wood disappear, but some bits are left behind: these bits are the ash.
This ash can be used for lots of things. It can be used in medicine to help cure illnesses or make things taste better. It can also be used in soil to help plants grow. So even though ashing might sound strange and scary, it can actually be very useful!