The episodic buffer has been added as an addition to the working memory model. It was added to explain the transfer of information about experiences between working memory and long term memory. The buffer communicates with long term memory and some components of working memory to connect functions of the central executive to long-term knowledge systems. The episodic buffer supplements and has greater capacity than the functions of the phonological loop and visuospatial sketch pad.
The addition of the episodic buffer allowed for the resolution to the problem of how information taken in at one particular moment will be remembered later on. It explains the "better-than-expected" performance of some tasks that is not completely explained by the phonological loop or visuospatial sketch pad alone.