Illustrators cannot stand alone. They don't have meaning except in conjunction with a verbal message. When someone puts out their hands to illustrate the size of the fish they caught, you know what their gesture means. A person who talks with their hands uses illustrators often. Their gestures would mean nothing apart from their communication, but are used to enhance their conversation.
Indicators reveal the speaker's internal state.
Common indicators are laughing, crying, and certain facial expressions. Regulators help to regulate interaction. We must be tuned in to regulating our conversations somehow in order to communicate effectively. We use regulators like eye contact, shifting position to face who's speaking, and head nods. Adaptors help a person adapt to stress or discomfort.