…“the relation between ‘things’, concepts and signs lies at the heart of the production of meaning in language. The process which links these three elements together is what we call ‘representation’.” 
—Stuart Hall

To represent something is:

1. 1. to describe or depict it (e.g. this painting depicts the crucifixion of Jezus Christ)
   2. to symbolize, stand for (e.g. in Christianity, the cross represents the suffering and crucifixion of Christ).

In his book ‘Representations: Cultural Representations and Signifying Practices’, Professor of Sociology Stuart Hall, defines two processes, two systems of representation.

1. The first is a classifying system; a “system by which all sorts of objects, people and events are correlated with a set of concepts or mental representations which we carry around in our heads.” (Hall, 2003, 16). This system consists of “different ways of organising, clustering, arranging and classifying concepts, and establishing complex relations between them. For example, we use the principles of similarity and difference to establish relationships between concepts of to distinguish them from one another.” (Hall, 2003, 16). Birds are similar to planes (both are ‘flying objects’) but different because one is part of ‘nature’ and the other is ‘man-made’.
2. Language (in the broad and inclusive definition; so not only written language, but also verbal, non-verbal, visual, sonic etc.) is the second system of representation involved in the process of constructing meaning. “Our shared conceptual map must be translated into a common language.” (Hall, 2003, 17). Via ‘signs‘ (the general term for words, sounds, images which carry meaning) we are able to we construct these concepts, get them out of our heads and share them with others.

“The relation between ‘things’, concepts and signs lies at the heart of the production of meaning in language. The process which links these three elements together is what we call ‘representation’.” (Hall, 2003, 18).