Many a times the URL looks like the following https://opensourcecook.in/index.php?page=blog&id=123
This type of URL does not convey any meaning to either the user of is useful for search engine, instead of these if we have something like https://www.opensourcecook.in/blog/post/iot/what-smart-device
The above URL clearly indicated that the it is a "blog post" with main topic "IoT" and with discussion about "What are smart Device".
When we install Drupal/WordPress it by default uses the clean URL. If the clean URL is not set in our web-server (Apache) then you will find it difficult to work with Drupal or many pages will show error. This post talks about how to enable clean URL