Filtration is commonly the mechanical or physical operation which is used for the separation of solids from fluids (liquids or gases) by interposing a medium through which only the fluid can pass. Oversize solids in the fluid are retained, but the separation is not complete; solids will be contaminated with some fluid and filtrate will contain fine particles (depending on the pore size and filter thickness).
In coffee brewing filtration is an essential step of the process, because it allows the separation of the coffee grounds from the beverage. Almost all coffee brewing methods use some sort of filtration. Most common filtration methods are the paper filter, the screen filter, and the filter basket. An example of brewing methods that does not use filtration is Turkish coffee.
The French press brewing method makes use of a course filter that only serves to filter out bigger particles.
These different types of filtration yield different results in the final cup. Filter coffee, with its finer filter, yields a much cleaner cup with no sediment and brighter tasting notes. The course espresso and French press filters allow more properties from the coffee bean into the beverage. Coffee brewed with these methods is therefore darker, fuller and more oily.