A European Currency Unit (also known as ECU) was an older type of currency that was used in Europe. It was created in 1979 to try and make trading easier. The ECU was not a physical coin or a paper bill like dollars or euros, but it was a type of money that people could use to buy or sell things. It was made up of different European currencies that were given values and traded against each other. For example, if you had a British pound, you could use it to buy an ECU, which you could then use to buy something from France or Germany. Eventually, the ECU was replaced by the euro in 1999, which is the current currency used in many European countries.