Goldback is a kind of money made from pure gold, which is a shiny yellow metal that people have been fascinated with for a long time.
Imagine you have a shiny golden coin in your toy box, just like the pirate's treasure! This coin is called a Goldback. But unlike a regular coin, it's not made of cheap materials like copper or nickel. Instead, it's made of pure gold, which is very valuable and is used to make jewelry, electronics, and other important stuff.
Now, you can't go out and buy your toys with Goldbacks, but they are used as money in some places where people really like gold. Some grown-ups who like to collect gold or invest in it, might use Goldbacks to buy things or save up for rainy days.
So, in summary, Goldbacks are a special kind of coin made from pure gold, that some people use instead of regular money to buy things or save for the future.