What is a view in Drupal? How do they work?

In Drupal, a view is a listing of information. It can a list of nodes, users, comments, taxonomy terms, files, etc. A view scans your website using any criteria you specify and presents the results in the format of your choice. Example formats include a HTML table, a RSS feed, a PDF document, a CSV document, an interactive map, an image slideshow, or a JSON representation to be used as a REST endpoint. The same content can be presented in multiple formats at the same time. For instance, you can present a table of user information and on the same page a link to download the data in CSV format.