The document discusses different types of signs, symbols, and visual codes that help people understand and interpret pictures. There are three main types of signs: symbolic signs which have no obvious connection to what they represent; iconic signs which visually resemble what they represent; and indexical signs which have a direct connection to what they depict. Visual codes also aid comprehension and include dress codes, color codes, and non-verbal communication through gestures and expressions. Understanding these signs, symbols and codes allows people to analyze pictures and derive meaning from them.