Representational is to do with being able to deal with different representations of data via a media type[0]. There is stuff about resource identification in ReST, but it's just about being able to address resources directly and permanently rather than the style of the resource identifier:

> Traditional hypertext systems [61], which typically operate in a closed or local environment, use unique node or document identifiers that change every time the information changes, relying on link servers to maintain references separately from the content [135]. Since centralized link servers are an anathema to the immense scale and multi-organizational domain requirements of the Web, REST relies instead on the author choosing a resource identifier that best fits the nature of the concept being identified.

[0] https://ics.uci.edu/~fielding/pubs/dissertation/rest_arch_st...