Shops selling items where some comparison is made before purchase, eg. clothing, footwear, household goods (furniture, carpets, electrical), recreational items, personal items.
The two major activities involved are: (1) merchandise shopping where checks are made on types of product, prices, advertised promotions and new items offered by competing stores; (2) service shopping where checks are made on the quality of selling and service offered by sales staff of competing stores.
Comparison shopping sites are a type of search engine that allow you to submit information about products; there may be a charge for submission and a charge per click.