With Views now in Drupal core as of D8 the two most common basic contrib modules from previous versions of Drupal, CCK and Views, are now both part of core.

CCK, now called Entities, from one perspective is what allows us to create arbitrary database tables through a web interface where we can hold arbitrary data yet work with it through a common interface, and use Drupal goodies like widgets, theming, content creation forms and pages, etc. on them. Views is the complement to this way of creating custom content. Views in core means we can now retrieve or query that arbitrary, custom content in arbitrary and custom ways.

Views is basically a web UI for an SQL query builder. The fields are the SELECTed database columns and the filters are your WHERE clause.

This isn't just a feature for non-technical dudes and non-developers. Just because you can write SQL queries doesn't mean you should write all of them. Views gives you an interface into various Drupal core and contributed modules and the content they manage, if those modules integrate with Views via hooks. Entities (or CCK) can create a mess of database tables. Sometimes these tables will change structure from under your feet due to some changes via the admin interface. You might not know until your code is broken. But using Views, the query will always be up to date.

Now that Views is in core, other parts of core could possibly depend on and build on Views, just like many other parts of Drupal core use concepts that came from Entities (CCK). So Drupal core can do a lot more out of the box. And contributed modules can be written to depend on only Entity and Views, which are part of core, and so these new modules won't have any other 3rd party dependencies. That's a win for module developers.