This document discusses different types of signs and symbols, including danger signs, codes, indexes, and symbols. It provides examples to illustrate the key differences between these sign types. Danger signs use pictures and words to convey a message, like warning about deep water. Codes use words, letters, or numbers in a system to identify or represent something, such as a date or age. Symbols have no obvious connection between the sign and what it represents. Indexes have a direct relationship to what they indicate and can represent larger concepts, like a tear representing feeling upset. Understanding these sign types relies on cultural knowledge and context.