Why there is a variable pop out automatically in Express?

As below, I didn't create the first 2 variables(first 2 lines), I don't know why they just came out there.

// Express
const { execFileSync } = require('child_process')
const { RSA_NO_PADDING } = require('constants')
const express = require('express')
const app = express()
const cookieParser = require('cookie-parser')

For template, I used PUG. Does it have something to do with PUG?

Thanks a lot!!