Interpersonal communication is usually described as a process of exchanging information or messages from a sender to a receiver through a specific medium. Among humans, exchange of information is usually done by using language which is defined as a system of codes made of arbitrary signals governed by certain rules of use to represent concepts or ideas. Communicating using language can either be written or spoken. This process of continuous sending and receiving of information from encoders to decoders is much easier to imagine when those who are involved in the exchange are capable of using language. However, what about in certain instances when a person has problems communicating? For example, take the case of an 8-year-old girl who has cerebral palsy spastic quadriplegia or a 45-year-old man who recently had a stroke which affected his ability to speak and move. They will not be able to move their lips, tongue or jaw to articulate words. They also will not be able to move their hands to write or type words. How, then, will they be able to communicate their needs such as to ask for help? Because of situations like these among people who are differently-abled, a new form of communication was developed. This recent development is commonly called Alternative and Augmentative Communication (AAC), and it usually makes use additional components as aids or supporting devices.

AAC devices as a medium of communication are highly unique and individualized relative to the person who is going to use it. Unlike other mediums which are not particular to whoever wants to make use of it, the characteristics of AAC devices need to correspond to the limitations of the user. Going back to the girl with spastic cerebral palsy, she cannot make use of a device that will require for her to speak or write but she can use of her sight to select pictures that will represent her needs. Since she cannot use her hands to point to the pictures but she can move her head minimally, a laser penlight can be attached to her head to be used as a pointer. In the case of the man who had stroke but still retained his ability to spell words, instead of using pictures, a complete set of alphabet letters can be used as the components for him to choose from. For people who cannot see and speak but still retained their sense of hearing, devices that produce sound signals representing certain concepts can be used.

Aside from the devices being highly individualized, they should also be portable, durable, flexible and easy to use. A device which is big and heavy is not easy to carry and will be difficult to transfer from one place to another. Devices that are not portable are more of a limitation rather than an aid to those who use them. AAC devices should also be strong enough to sustain being used for a long time. Keeping on buying or making new AAC devices that easily break or get destroyed can be expensive and impractical. It is advantageous if a device can be upgraded or easily altered to suit the changes in the user's skills. For example, if a child progresses from using two words to using sentences to convey messages, the device should also be able to adapt to this development. Finally, devices should not be complicated. People who will use these device have limitations and too much unnecessary buttons or icons may just be confusing to them. If the device were compared to a written document, the term to be used is being "concise". Also, it should be taken into consideration that these devices should be easy to manipulate because any more difficulty can be tedious for the user.

Nowadays, AAC devices range from those that are low-tech such as pictures that can be attached to boards using fasteners (e.g. Velcro) to those that utilize high-technology components such as laptops or portable PCs with access to the Internet. Several companies already market AAC devices but, if preferred, devices can still be made personally. It is understandable that some devices are quiet expensive especially those that make use of complex components which is why most individuals who have financial limitations opt to make their own devices. Those that are created personally, however, still need to be tested or observed for their effectiveness. Modifications can be later applied if the devices are found lacking in some ways.

The goal of using alternative and augmentative communication devices is to help a person achieve the natural way of communication through the use of aids. As their name suggests, these devices are just used to augment and as alternates and not to totally replace the natural and more ideal form of communication. Through the use of these device, professionals involved with rehabilitation still aim to help the person gain or regain the ability to communicate using language and speech.