The flag that we associate with pirates - the skull and crossbones on a black background, known as the Jolly Roger - was not in fact used often by pirates in the past. There are other flags of the same kind, for example the hourglass Jolly Roger (the hourglass was a symbol of death seen in some 17th century paintings, with the sands representing life running out). But in fact most 17th and 18th century pirates used a simple black flag, and those who did use the skull and crossbones - such as the notorious John Taylor and Edward Engand were noted for doing so rather than being typical.

The first known use of the Jolly Roger is at the beginning of the 18th century. Before that, pirates may have used a red flag to warn or frighten people into surrendering.

You can learn more about pirate flags here.