Drupal has a flexible permissions system based on roles. Users are assigned one or more roles, and each role is granted specific permissions defined by modules.
Go to People then Permissions to see every permission in the system. Each module adds its own permissions covering things like creating content, editing other users, and accessing admin pages.
Permissions are grouped by module, making it easy to find the ones you need. You can also create custom roles for different user types like editors, authors, and administrators. For fine grained access control beyond simple permissions, use modules like Group or Workbench Access. These add concepts like content ownership, section based editing, and hierarchical permissions. Drupal’s permissions system is one of its greatest strengths and a key reason it remains popular for sites with complex user needs.