A Separation process to separate Solids from Fluids in a Mixture (liquids or gases) by adding a medium through which only the fluid can pass.

https://www.wikiwand.com/en/Filtration

http://www.bbc.co.uk/education/guides/zgbqtfr/revision/8

When a product is made as a solution, one way to separate it from the solvent is to make crystals. This involves evaporating the solution to a much smaller volume and then leaving it to cool. As the solution cools, crystals form, and these can be obtained by filtration.