Drupal localization is built on top of gettext, the GNU internationalization and localization (i18n) library.
Drupal can automatically notify the administrator about new versions of modules, themes, or the Drupal core.
In a Drupal website's default configuration, authors can contribute content as either registered or anonymous users (at the discretion of the administrator).
This content is accessible to web visitors through a variety of selectable criteria.
If there is any error shown after update or new updates is not compatible with a module, then it can be quickly replace by backup.
This increases flexibility and security and allows administrators to cleanly upgrade to new releases without overwriting their site's customizations. Themes adapt or replace a Drupal site's default look and feel.
(Starting with version 8, core is kept in its own 'core' sub-directory.) Drupal core is the stock element of Drupal.
Bootstrap and Common libraries are defined as Drupal core and all other functionality is defined as Drupal modules including the system module itself.
Prior to version 7, Drupal had functions that performed tasks related to databases, such as SQL query cleansing, multi-site table name prefixing, and generating proper SQL queries.
In particular, Drupal 6 introduced an abstraction layer that allowed programmers to create SQL queries without writing SQL.