app.set('port', 8080) is similar to setting a "variable"
8080, which you can access later on
app.get('port'). Accessing your website from the browser
will really not work because you still didn't tell your app to listen and
app.listen(8080) on the other hand listens for connections
8080. This is the part where you're telling your app
to listen and accept connections. Accessing your app from the browser using
localhost:8080 will work if you have this in your code.
The two commands can actually be used together: