This sets up an event listener for any GET request that comes into the server with the path of `/`. Give it a callback function which takes a request variable and a respond variable. Each of these have different methods/properties which we'll learn about
## Middleware
We can define a callback function that is called or all requests and then continues on to other request handlers
```javascript
app.use(function(req, res, next){
console.log('middleware');
next();
})
```
`next();` tells express to continue processing the request. `app.get(),app.post()`, etc have this ability too, but it's rarely used.
Just like with `app.get(),app.post()`, etc we can add the ability to handle just those requests that match a url pattern
```javascript
app.use('/foo', function(req, res, next){
console.log('middleware');
next();
})
```
## MVC
One of the main goals of express is to cleanly separate data from the view layer. To do this, it follows the Model View Controller pattern, which creates a middleman (Controller) which passes data (Models) off to the presentation/html (View) layer
