Content Types - Basic structure for different types of content.
Blocks - Manage and place blocks in regions of your theme.
Views - Create dynamic lists of content.
Fields - Define reusable data types for content types.
Taxonomy - Categorize and tag content.
Nodes - Individual pieces of content.
Roles and Permissions - Manage user roles and their permissions.
Regions - Areas in a theme where blocks can be placed.
Themes - Customize the look and feel of your site.
Modules - Extend Drupal's functionality.
For more thorough and version-specific information, it is advised to consult the official Drupal documentation, to which this cheat sheet just serves as a fast reference: Documentation for Drupal.