Filtration is a process used to remove an insoluble solid material from a solution. The solid could be the required product or an impurity or an additive such as a drying agent.
The mixture is poured onto a filter, usually a filter paper, that acts like a sieve and allows the passage of liquid, the filtrate, while the solid, the residue, collects in the filter.
You can find out more about the various methods of filtration here.
