Digital currencies such as bitcoin are electronic forms of currency that can be used to make purchases online. The document discusses what digital currencies and bitcoin are, as well as their benefits like enabling instant purchases and being impossible to counterfeit. However, they also have disadvantages like volatility and lack of development. The central bank of Egypt warns against using digital currencies and Al-Azhar and Dar al-Iftaa have forbidden them as they are not backed by tangible assets and lack regulation. In conclusion, the author initially thought digital currencies could be the future but now believes they will not due to issues like wasting energy and becoming cheap if centralized.