Symbols are images that encapsulate the essence of whatever they represent. When you see one, you instantly understand something fundamental about what the symbol stands for. Historically, witches and occultists have also used symbols to protect secret knowledge from people who aren't ready to receive it. Therefore, many spells and rituals employ a variety of symbolic gestures, patterns, objects, colors, etc. Symbols speak directly to the subconscious, which understands pictures better than words, even if your rational mind doesn't.