A symbol is a picture that represents or stands for something. It does not have to be accompanied by words, for it has meaning of its own. Symbols can also evoke emotions. This is a picture that is not a symbol. Though this is a symbol, you most likely don't know what the symbol represents.
Symbols get their power by being a visual representation of a meaning.
If you don't know the meaning, no amount of staring at the symbol will bring forth the meaning. This is a recognizable symbol. It represents copyright. If you knew what the symbol represented, its meaning should have been instantaneous. Most likely not.