A filter is called an “AC” or air conditioning filter if it’s used in a cooling or air conditioning application. An AC filter traps particles in the air before they enter the AC system. It catches dust, pollen, mold spores, and pet dander so they don't circulate through the house It also protects the air conditioning coil and other cooling components from a build-up of dirt, grime, and other airborne particles.
AC filters can be made of various materials, from fiberglass mesh in a cardboard frame to pleated synthetic fabric in a beverage board frame. As air passes through the porous filter, larger particles get stuck in the fibers or folds. Clean air then flows into your AC unit and eventually into your home.