Hi, I am reading express docs and can't understand this line (highlighted in red) can anyone help?

const express = require('express') const app = express() const port = 3000 app.get('/', (req, res) => res.send('Hello World!'))app.listen(port, () => console.log(`Example app listening on port ${port}!`)) I understand that we are sending a GET request but why passing req and res as arguments?

Submitted November 16, 2019 at 11:34AM by Ok-Use