Rare stamps are unique postage stamps that are highly sought after by collectors due to their limited availability, historical significance, or printing errors. These stamps can be valuable, sometimes fetching thousands or even millions of dollars at auctions. Examples of rare stamps include the British Guiana 1c Magenta and the Inverted Jenny from the United States. Collectors often seek rare stamps to complete their collections or as an investment. The rarity can be determined by factors such as the number of stamps printed, the condition of the stamp, and its provenance. Many rare stamps are preserved in protective cases to maintain their quality and value.