# Source: https://mikro-orm.io/docs/fundamentals.md

## [📄️<!-- --> <!-- -->Defining Entities](https://mikro-orm.io/docs/defining-entities.md)

[Entities are simple javascript objects (so called POJO) without restrictions and without the need to extend base classes. Using entity constructors works as well - they are never executed for managed entities (loaded from database). Every entity is required to have a primary key.](https://mikro-orm.io/docs/defining-entities.md)