On top of the funnel-shaped part there is a cylinder with a fritted glass disc/perforated plate separating it from the funnel.

The liquid to be filtered is poured into the cylinder and drawn through the perforated plate/fritted glass disc by vacuum suction.

The main advantage in using this type of filtration is that it proceeds much more quickly (several orders of magnitude) than simply allowing the liquid to drain through the filter medium via the force of gravity.

However, it is often the case that further drying is required, by an oven or other means, in order to remove as much residual liquid as possible.

A vacuum tight seal and stability of the Büchner flask and filter are essential during the filtration process.