In Drupal 8, an entity is a powerful and flexible object that represents a piece of data or a content item. Entities are the building blocks of Drupal’s data model and are used to store, manage, and manipulate different types of data, including content, configuration, and user information. Understanding entities is essential for working with Drupal 8’s data architecture. Here are the key aspects of entities in Drupal 8:

1. Entity Types:
– An entity type represents a specific kind of data or content in Drupal 8.
– Drupal core provides various entity types such as nodes, users, taxonomy terms, comments, and files.
– Custom entity types can also be defined by modules or developers to represent new data structures.

2. Entity Structure:
– Each entity has properties and fields that define its structure and data.
– Properties are basic data elements of an entity, such as its ID, creation timestamp, or author.
– Fields are flexible and allow additional data to be attached to the entity.
– Field types can include text, numbers, dates, references, and more.
– Entities can have multiple fields, which can be customised based on the entity type.

3. Entity Storage:
– Entities are stored in the database using Drupal’s Entity API.
– The Entity API provides a unified way to interact with entity data, regardless of the underlying storage system.
– Each entity type has its own storage handler responsible for persisting and retrieving data from the database.
– Entity storage supports multiple storage backends, including the default SQL-based storage and other contributed storage modules.

4. Entity CRUD Operations:
– The Entity API provides a set of methods for performing Create, Read, Update, and Delete (CRUD) operations on entities.
– Developers can use these methods to create new entities, load existing entities, update entity data, and delete entities programmatically.
– For example, creating a new node entity involves using the appropriate entity constructor, setting its properties and fields, and saving the entity.

5. Entity Display and View Modes:
– Entity view modes control how an entity is displayed to users.
– Drupal 8 introduces the concept of view modes for entities, which determine how entity data is rendered and presented.
– View modes allow developers and site builders to define different display configurations for various contexts, such as full view, teaser view, or custom view modes.

6. Entity Hooks and Events:
– Drupal 8 provides hooks and events to allow modules to react and modify entity operations and data.
– Hooks like `hook_ENTITY_TYPE_presave()`, `hook_ENTITY_TYPE_insert()`, and `hook_ENTITY_TYPE_update()` are invoked at specific points during entity processing.
– Developers can implement these hooks to perform custom logic before or after entity operations.

Entities in Drupal 8 provide a flexible and extensible way to store and manage data. They can represent various types of content and information, and their structure and behavior can be customized to fit specific requirements. By leveraging entities and their properties, fields, and storage mechanisms, developers can create robust and scalable Drupal applications with rich content management capabilities.