... I stumbled across this article a few weeks back - I think it was on Gizmodo ( http://gizmodo.com/ ) - And it compared the literal definition of a logo versus a symbol...The premise was that most people (...yes, myself included) are using these terms incorrectly - They have different meanings; it is true that both are graphic representations of companies, sports teams, user interface functions for electronics, etc...
BUT...They are not interchangeable.
Here is the distinction: A logo contains BOTH graphics and text...A symbol? - Well, a Symbol has no text.
Interesting, right?
... So, what that means is when people refer to things like Apple's iconic - Well, Apple, with the bite taken out of it - Or Jordan Brand's "Jumpman" as a logo they really are mistaken. Those graphics are in fact actually symbols - Because just like the Bat Symbol they do not contain any text.
In the same vein - Here is a link to Ready Mag's website and a quick piece they did on the origins of certain well known user interface symbols - It is a quick read and in my opinion pretty interesting to see the background on some of the symbols we use and interact with every day while on our computers, tablets, televisions and smart phones...
Hot Mama