Persistent data structure

A persistent data structure is a type of data structure that keeps its data even after it has been changed. So, if you change the data, it will remember the change after it has been made. This is useful because it means you can store data that doesn't go away when you make changes to it. For example, if you have a list of names and you need to add another person to it, you can do that and the list will keep its original form even after the new person has been added!