This is the slow passage of a liquid through a porous mass.

In coffee, percolation methods are extraction methods referred to as “pour over”: v60, chemex, kalita wave, melitta, fellow stagg, etc.
These methods involve water passing through the ground coffee, using only the force of gravity.
The extracted liquid is filtered, usually through paper or micro-perforated filters, and gathered in a container at the base of the percolation system.