🔹 1. req.params → Route Parameters

• Used in the URL path itself.
• Defined in Express route like: /user/:id
• Used for identifying a specific resource

Example:

app.get('/user/:id', (req, res) => {
  console.log(req.params.id); // e.g., '42' from /user/42
});

🔹 2. req.query → Query Parameters

• Used in the URL after the ?
• Used for filters, sorts, searches, optional values

Example:

// URL: /search?keyword=books&page=2

app.get('/search', (req, res) => {
  console.log(req.query.keyword); // 'books'
  console.log(req.query.page);    // '2'
});

🔹 3. req.body → Request Body

• Used in POST/PUT/PATCH requests
• Carries form data or JSON
• You must use middleware like express.json() or express.urlencoded() to access it

Example:

app.use(express.json());

app.post('/login', (req, res) => {
  console.log(req.body.username); // from POST body
  console.log(req.body.password);
});