These may add emphasis or shades of meaning to what people say. Some definitions limit this to verbal communication that is not words.
Body language, gestures, facial expressions, tone and pitch of voice are all examples of paralinguistic features.
In the classroom
Paralinguistic features of language are extremely important as they can change message completely. Tone and pitch of voice is commonly dealt with at all language levels, but a fuller consideration of paralinguistics is often left to very advanced courses.