A symbol is something that represents an idea, a process, or a physical entity. The purpose of a symbol is to communicate meaning. For example, a red octagon may be a symbol for "STOP". On a map, a picture of a tent might represent a campsite. Numerals are symbols for numbers. Personal names are symbols representing individuals. A red rose symbolizes Love and Compassion.
The word derives from the Greek symbolon meaning token or watchword. It is an amalgam of syn- "together" + bole "a throwing, a casting, the stroke of a missile, bolt, beam." The sense Evolution in Greek is from "throwing things together" to "contrasting" to "comparing" to "token used in comparisons to determine if something is genuine." Hence, "outward sign" of something. The meaning "something which stands for something else" was first recorded 1590, in Edmund Spenser's Faerie Queene.