A proxy card is a ‘stand in’ card for an original Pokemon card. Proxies are very useful for collectors and players alike.  A common reason that people may buy pokemon proxy cards is because the original cards are out of reach in terms of price. For example first edition Pokemon cards can cost thousands of dollars.  Another reason to buy proxies is to use in gameplay so your original cards don’t get damaged or bent.  Finally, pokemon proxy cards allow playtesting without needing to invest in or purchase cards before knowing if they will work in a deck.