Representational systems also known as sensory modalities and abbreviated to VAKOG is a postulated model from neuro-linguistic programming. It is nothing but a collection of models and methods regarding how the human mind processes and stores information. The central idea of this model is that experience is represented in the mind in sensorial terms, i.e. in terms of our five senses
According to Bandler and Grinder our chosen words, phrases and sentences are indicative of our referencing of each of the representational systems. So, for example, the words "black", "clear", "spiral" and "image" reference the visual representation system; similarly the words "tinkling", "silent", "squeal" and "blast" reference the auditory representation system.
Bandler and Grinder also propose that ostensibly metaphorical or figurative language indicates a reference to a representational system such that it is literal. For example, the comment "I see what you're saying" is taken to indicate a visual representation.
Further, Bandler and Grinder claim that each person has a "most highly valued" (now commonly termed preferred) representational system in which they are more able to vividly create an experience (in their mind) in terms of that representational system, tend to use that representational system more often than the others, and have more distinctions available in that representation system than the others.
So, for example, a person that most highly values their visual representation system can easily and vividly visualise things and tends to do so in preference to creating or recreating an experience in terms of the other representational system.
Representational systems are one of the foundational ideas of NLP and form the basis of many NLP techniques and methods.