Variable-length array

A variable-length array is like a kind of special list. It's like a regular list that you can change and update, but it's more like a data structure. It's like a box you can put things into, but the box can be different sizes. It's like a list of different sizes. You can ask it how big it is, and it can tell you, and then you can add or take away things from the list. So if you need a lot of things, it can get bigger, and if you don't need so much, it can get smaller.