Filtration is a method of physical or mechanical separation of one substance to another in a solution. This can be very effective in separating suspension for example sand and oil using a filtering devise that traps the larger compound thus letting the smaller substances get in. Let me show you a simple example of filtration and how it works.
Consider a mixture of water and sand. Using a properly folded filter paper in the funnel, pour out the contents of the mixture while being guided by a glass rod. Be sure that there is container (a beaker) to capture the contents after pouring. Anything that passes through the filter paper is called the filtrate. Apparently, anything that has remained in the funnel is called the residue.