(I'm investigating various questions including of STWM, ideas, and networks or clusters of ideas.)
https://en.wikipedia.org/wiki/Chunking_(psychology)
It's like a grocery bag for ideas. The more familiar they are the more you can represent them with a single abstract concept in your working memory that basically acts as a pointer to the various items contained in the concrete implementation.
Here's another reference you may enjoy:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2657600/
What is STWM?
STWM: short-term working memory. A fascinating presentation by Sander van der Leeuw on the interactions of that and anthropology: https://m.youtube.com/watch?v=80dR9Q2glgY