There are three main types of signs: iconic signs resemble the object they represent like photographs, indexical signs have a direct connection to the object like a black cloud indicating rain, and symbolic signs connect to the object through learned cultural meanings like a rose representing romance. There are also three types of music videos: illustrative videos directly visualize the song lyrics, amplification videos increase the meaning of the lyrics visually, and disjuncture videos ignore the lyrics and have no relevance to the music. Synesthesia is a concept where people see images when hearing music, like visualizing what a music video might show before watching it.