how to route to a different page express code example

Example 1: route parameter in node

var express = require('express');
var fs  = require('fs');
var app= express();
 app.get('/index/profile/:id',function(req,res){
    //  res.send('profile with id' + req.params.id)

    
    
 });
app.listen(3000,'127.0.0.1');
console.log('lsitng');

Example 2: express() vs express.router()

var express = require('express'),
    dogs    = require('./routes/dogs'),
    cats    = require('./routes/cats'),
    birds   = require('./routes/birds');

var app = express();

app.use('/dogs',  dogs);
app.use('/cats',  cats);
app.use('/birds', birds);

app.listen(3000);