How does charcoal filtration work?

basically there is a bunch of little tiny pieces of charcoal put into a big or small air/water tight tube with a water inlet and outlet. the water goes in and runs through the charcoal which in turn filters, "soaks up", alot of the impurities/particles in your water. then your water looks clearer and has no more or less floaty stuff in it. but be careful those water systems are really overpriced.