# Understanding Stacks

In computer science, a stack is what you think it is. A pile. There are two important restrictions:

1. Only add to the top
    
2. Only remove from the top
    

To illustrate, let’s track how we get dressed using a stack. At first, the stack is empty. Let’s add a `shirt`, a `sweater`, and a `coat`. Our stack now looks like this:

```mermaid
flowchart TD
coat ~~~ sweater ~~~ shirt
```

Now, we want to go swimming. In real life, and in a stack, we can’t remove the `shirt` first since the `sweater` and `coat` are in the way. The stack we built tells us the order in which to remove the clothes: `coat`, `sweater`, `shirt`.

The only thing we can access is the last thing we put in. Therefore, we say that a stack is last-in, first-out (LIFO). We could also call it first-in, last-out (FILO), but nobody says that.

You can read more at [https://www.geeksforgeeks.org/dsa/applications-advantages-and-disadvantages-of-stack/](https://www.geeksforgeeks.org/dsa/applications-advantages-and-disadvantages-of-stack/).