An important fact about anodes and cathodes is that chemical processes will occur when they are submerged. For example, electrolysis occurs when electrodes are dropped into salty water. (The water has to be salty so that it will conduct electricity.) The chemical process created causes oxygen to be released from one electrode, and hydrogen from the other.

The process at the anode is called oxydation, and the process that occurs at the cathode is reduction. A good nmemonic for the whole thing is the sentence, "An ox and a red cat".

This finds practical application in many areas, and one known to most people (whether they know it or not) involves the "zincs" on a boat. They are pieces of sacrifical metal performing as the anode in cathodic protection, creating a beneifical electrical field to keep the propellers from corroding away.