According to the Autism Community Foundation, AAC (Augmentative and Alternative Communication) are defined as multiple methods in helping enhancing and aiding someone struggling with speech.  

Usually, the AAC are practiced using pictures, as individuals with autism tends to think and memorize through vision. Some of the most common practices are, the usage of flashcards with pictures and electronic devices. These tools "helps give the individual a more clear and concrete understanding of what to say or is being told". AAC is also useful in measuring one’s comprehension and strength in language, and so help therapists, teachers, and parents know what specific areas to work on helping improve speech.