Sometimes posts just write themselves.
Literally copy-and-pasted from Wikipedia.
I kid you not.
*****
The word error has different meanings in different domains. The concrete meaning of the Latin word error means "wandering" or "straying", although the metaphorical meaning "mistake, misapprehension" is actually more common. To the contrary of an illusion, an error or a mistake can sometimes be dispelled through knowledge (knowing that one is looking at a mirage and not at real water doesn’t make the mirage disappear). However, some errors can occur even when individuals have the required knowledge to perform a task correctly. Examples include forgetting to collect your change after buying chocolate from a vending machine, forgetting the original document after making photocopies, and forgetting to turn the gas off after cooking a meal. These slip errors can occur when an individual is distracted by something else.
Baseball
In baseball, an error is judged by the official scorer when a runner advances a base because of a fielding mistake, and perfect play would have prevented the advancement, and the mistake was physical. Mental misjudgments are not errors. Failing to get more than one out on a given play is not an error. Application of this rule is necessarily subjective. See error (baseball).
Perfect Pitch 
ahahahahaha, I have to tell you this is one of my favorite MLBlogs posts ever. Although I do hope it was not too tragic.
Mark/MLB.com
http://mlblogs.mlblogs.com