Percolator Bongs or Perc bongs have an extra filter inside the main chambers. Which is located either within the tube that your mouth sits on or inside the water pipes or bong.
You can find a lot of different designs of the Percolator Bongs & Perc bongs. Realistically they all do the same thing. Simply the basic use is the same, Water and your good weed smoke are pushed through the percolator tubes. Then by pressure from you giving a big suck. This first step really advances the transfer of heat. The smoke weed is cooled down by the bubbling of the water. Then the second action helps the rough smoke go into finer particles allowing for a better and smoother smoke.
This also has a great influence on filtering those bad particles/carcinogens and other nasty little things out of your smoke.
After all the actions. The smoke going through all those actions in the Percolator Bongs. Will give you a Nice cool hit every time and hits the spot just where you want it.