What are the key differences between using `req.query` and `req.params` in Express.js for retrieving data from a client request, and when is each appropriate?

`req.query` and `req.params` in Express.js are used to retrieve data from a client request, but they access different parts of the URL and serve distinct purposes. `req.query` is used to access query parameters in the URL. Query parameters are appended to the URL after a question mark (?) and are typically used for optional data, filtering, sorting, or pagination. They are key-value pairs separated by ampersands (&). Example: `/products?category=electronics&sort=price....