A Corruption (also called a Corruption effect) is a buff that is applied (typically self-applied) to a mob or creature. Corruptions can be removed using Corruption Removal Skills, of which all Character classes have at least one.
Many boss fights in instances and raids require efficient and timely Corruption removal in order to be successful. Corruptions can be recognized by "Resistance: Corruption (Level)" in the effect tooltip.
The following dropdown menu shows a list of specific corruption effects. This list may not be complete.