A repertory extraction contains the data from a repertory but instead of being arranges in sections and rubrics, it's arranged in Remedies and Rubrics. You open a remedy and all of the rubrics where that remedy is found will be shown in a list. This is used in MacRepertory Keynotes, for example Boenninghausen's Extraction, Boericke's Extraction, Clarke's Extraction, Kent's Extraction, and Knerr's Extraction.