serving static page from file in express code example

Example 1: express public

app.use(express.static(__dirname + '/public'));

Example 2: app.use public

app.use(express.static('public'))
app.use(express.static('files'))

Example 3: app.use public

express.static(root, [options])

Example 4: static file

Static file is any content that can be delivered to an end user without 
having to be generated, modified, or processed.