Ecuador uses the U.S. Dollar. In change, you will most likely receive both U.S. minted coins as well as Ecuadorian minted coins. However, all paper currency will only be U.S. You should pay particular attention to the fact that denominations over a $20 bill will be exceptionally difficult if not impossible to use in general. You may have to visit a bank to get it changed. Ecuadorian businesses often do not have banks of money on hand, so even a $20 bill can make it difficult for a business owner to make change.
US coins used are the penny, nickel, dime, quarter, half dollar and most often $1 coins. The $1 coins that never caught on in the US has found a thriving acceptance here in Ecuador.
Numbers are important to know for innumerable reasons.