Decantation is the process of separating the liquid portion of a mixture when the heavier component settles as sediments at the bottom. In other words, it is the process of moving a liquid from one container to another while leaving the sediments at the bottom alone.
As an example: Sand settles at the bottom of a container when a mixture of sand and water is allowed to stand. The upper portion of the container contains water. This can be separated from the sand at the bottom simply by pouring it into another container without the use of any other separating device. This is referred to as decantation.