### **Observer Pattern**

**Description:**
The Observer Pattern establishes a one-to-many dependency between objects so
that when one object (the subject) changes state, all its dependents (observers)
are notified and updated automatically. This pattern is essential for
implementing distributed event handling systems.

**How and When to Use It:**
- **When to Use:** Use the Observer Pattern when changes to one object require
changes to others, and you want to avoid tight coupling. It's ideal for
implementing event systems.

- **Example:** In a real-time data dashboard, when the underlying data model
updates, all views subscribed to the model are automatically refreshed to
reflect the new data.