In this lesson, we will explore the concept of many-to-many relationships in databases and their implementation in Django. A many-to-many relationship allows multiple records in one table to be associated with multiple records in another table. This type of relationship is crucial for various real-world applications, such as connecting tags to tasks where a single task can have multiple tags and a single tag can be associated with multiple tasks.

By the end of this lesson, you will be able to:

• Define models in Django that use many-to-many relationships.
• Create serializers to handle these relationships.
• Load initial data using fixtures.
• Write unit tests to verify many-to-many relationships.

Imagine you want to implement adding tags for your todo items. You can add multiple tags to each todo item, and each tag can be added to multiple todo items. This is called a many-to-many relationship.

We'll use two models: Tag and Todo. Each Todo task can have multiple Tags, and each Tag can be associated with multiple Todo tasks. We achieve this in Django using the ManyToManyField.