NID (Node ID) is a unique identifier used in Drupal CMS to identify a node. A node is a piece of content, such as an article, page, or blog post, that is stored in the Drupal database. The NID is a numerical value that is assigned to each node when it is created. It is used to reference the node in the database and to access the node's content.

The NID is an important part of the Drupal architecture and is used in many different ways. For example, it is used to create links between nodes, to create relationships between nodes, and to access the node's content. It is also used to create URLs for nodes, to create menus, and to create views.

The NID is also used to identify nodes in the Drupal database. This allows Drupal to quickly locate a node and retrieve its content. It is also used to identify nodes in the Drupal cache, which helps to improve the performance of the website.

The NID is an important part of the Drupal architecture and is used in many different ways. It is important to understand how the NID works in order to effectively use Drupal CMS.