Gelt is a cashback app in Spain that offers to refund money to its users and provides valuable market data to associated brands. In addition to Spain, Gelt is the first cashback system in Argentina, Brazil, Colombia, and Mexico. It offers cashback on groceries and additional opportunities to earn money by completing surveys, challenges, and online offers outside of supermarkets. Gelt aims to help users earn money through various methods, including smart shopping, gift cards, surveys, and more.