Any form of communicating and expressing thoughts and feelings that isn't talking might be considered augmentative and alternative communication.
Often, AAC is differentiated as aided and unaided systems, and people may use any combination of these at different times to communicate.
"You do not need anything but your own body to use unaided systems," which include "gestures, body language, facial expressions, and some sign vocabulary," according to the American Speech-Language-Hearing Association (ASHA).
"Aided AAC systems use an external tool or device, electronic or otherwise. Aided AAC systems are sometimes split into low and high tech systems," according to Research Autism.