Pleating describes a flat sheet of material folded multiple times to increase the surface of the media around a cartridge core. This kind of arrangement increases the filtering area, increases the flow handled and decreases the differential pressure.
The main filtration process in this type of filter is made in the surface (every filter, in some degree, is a depth filter due that in the matrix there will always be some contaminant retention).
Pleated filters commonly come in cartridge type filters.
