What is a "Holders/Sujetadores de Sujecion"?
I think you are referring to the black plastic clips that come with the assorted pegboard hooks from Home Depot.  "Sujetadores de Sujecion" is Spanish for "Fastening Clips". These are placed over the hook to hold it to the board - this is useful for the single hole hooks that tend to come out easily. I found that these do not fit all pegboards.  They are not essential by any means.