How does a marine aquarium skimming pump work?

There is an airline that sucks air in due to the pumps output of water. The water being forced out is now combined with air which is then diced by an impellar which is modified to give finer micro bulbs. These bulbs are what manufacturers want for more air contact with the water surface. Pollutants (skim) is then created. Sorry for the generic concept but I don't know the big lingo. Hope that helps.