body parser understand code example

Example: body parser

<script>
const bodyParser = require("body-parser");

app.use(bodyParser.urlencoded({extended:true}));
  
app.post("/", function(req, res){
  let firstName = req.body.fNAME;
  
});
</script>

<input type="text" name="fNAME" placeholder="First Name">