Views is defined on the Drupal website as:
…essentially a smart query builder that, given enough information, can build the proper query, execute it, and display the results.
What this means is that by using instructions from you, as supplied through the comprehensive Views user interface, Views builds up MySQL queries that it runs against the Drupal database to return whatever information you require. This could be a list of the latest articles sorted by date, it could be all the content on the site that contains a specific term, or it could be the titles of all the newest pages in a given book linked to their node. Pretty much anything you want.
Because Views offers such a wide range of possible query options, the user ...