Icons are scattered throughout our history as a species; early man painted pictures onto stone depicting their triumphs over their hunted prey, Egyptians had an icon-based writing system in their hieroglyphics, and in the early church the symbol of a fish represented a Christian meeting place or tomb. Icons have always served a definitive purpose throughout mankind's history on this planet: to inform and instruct.
Icons are still prominent today in our everyday lives, as they serve the same purpose as they always have. As the craftsmen of the Web industry, we must ensure that we use correct representations of actions to inform users of their consequences.
As the Web has evolved over the years, we have established a (fairly) standard set of icons — a trash can or a cross has come to represent deleting or removing something; an envelope has become the indicator for a message or mail. These are little visual cues to help people along their way. Some icons have established such strong associations that they can exist on their own without supporting text, meaning, they can remove language barriers to form their own universal language. We need to use the right icons to communicate the right things.