I'm working on Nodejs and using "Express js" and now I'm working on "Middleware Functions" and this is my current code

const express = require('express')
const app = express()

const myLogger = function (req, res, next) {
  console.log('LOGGED')
  next()
}

app.use(myLogger)

app.get('/', (req, res) => {
  res.send('Hello World!')
})

I'm confused about the "next" parameter and I have the following questions about the middleware function

1. What is the use of "next"? Is this a redirect to the "next middleware function"? What if so?
2. What happens if there is no "second middleware"?
3. What happens if we don't use "next"?
4. Can we redirect to custom middleware within "next"?