A Field Bundle is a type of entity in the Drupal content management system (CMS). It is used to group related fields together, allowing them to be managed as a single unit. This makes it easier to manage content and create relationships between different pieces of content. Field Bundles are also used to create custom fields, which can be used to store additional information about content.

Field Bundles are created by adding fields to a bundle. Each field can be configured to store different types of data, such as text, images, or numbers. The fields can also be configured to accept different types of input, such as text boxes, checkboxes, or radio buttons. Once the fields are added to the bundle, they can be used to create content.

Field Bundles can be used to create relationships between different pieces of content. For example, a Field Bundle can be used to create a relationship between a blog post and its comments. The blog post can be linked to the comments by creating a field in the Field Bundle that stores the comment's ID. This allows the blog post to be linked to the comments, allowing the comments to be displayed on the blog post page.

Field Bundles are a powerful tool for managing content in Drupal. They allow content to be organized into related groups, making it easier to manage and create relationships between different pieces of content. Field Bundles can also be used to create custom fields, which can be used to store additional information about content.