Short answers, pulled from the story.
The word symbol derives from the Greek symbolon, rooted in a verb meaning "put together" or "compare." It passed through Latin and Middle French before entering English, where the meaning "something which stands for something else" was first recorded in 1590 in Edmund Spenser's Faerie Queene.
The academic study of symbols is called semiotics. Semiotics examines signs, symbols, and signification as communicative behavior, focusing on the relationship between the signifier and the signified, and drawing connections to linguistics and psychology.
Carl Jung distinguished a sign as something that stands for a known referent, the way a word represents its object. A symbol, by contrast, points toward something unknown that cannot be made fully clear or precise. He used Christ as an example of a symbol representing the archetype he called "the self."
Paul Tillich argued that symbols are born and die. A symbol becomes dead when it loses its meaning and power for an individual or culture. He also warned that when a symbol becomes so identified with the deeper reality it points to that the two are collapsed together, it becomes idolatrous.
Map symbols are grouped into five categories: pictorial symbols that resemble real-world features, functional symbols that represent activity at a place, conceptual symbols that represent a related idea, conventional symbols recognized through common use rather than intuitive connection, and abstract or geometric symbols chosen arbitrarily by the cartographer.
The meaning of a symbol is not inherent in the symbol itself but is culturally learned. A documented example is the symbol "x," which is used to mark "yes" in English-language surveys but typically means "no" in Chinese convention, producing opposite readings from the identical mark.