The Entity API is Drupal’s system for working with content and configuration. Entities represent everything from nodes and users to taxonomy terms and comments. They all use the same underlying API for loading, saving, and querying.
You interact with entities through the entity type manager service. For example, you can load a node by ID, modify its fields, and save it back with just a few lines of code.
The Entity API is the recommended way to work with data in modern Drupal. It handles caching, validation, access control, and hooks automatically. Writing raw database queries to create or modify entities bypasses important safeguards and is discouraged. Learning the Entity API well is one of the most valuable investments a Drupal developer can make. It applies to nearly every task that involves reading or writing content.