It really depends on what filters you have.....internal (the unit sits inside your aquarium), external, (The unit sits beside or under your tank) or undergravel (sits under the gravel in your tank)
Generally speaking, both internal and external filters will require cleaning roughly once a month. They usually have re-usable filter media which includes a sponge or filter wool, some ceramic or plastic biological media and maybe some carbon.
The sponge and ceramic media will need rinsing in old fish tank water....usually done when you're doing a water change. Do not wash it in tap water as the chlorine will kill all the good bacteria.
If you have carbon, you can either replace it with some new carbon or you can replace it with more biological bacteria....it doesn't really matter which you do.
Hope this answers your questions...if not, please ask again.