Design patterns are descriptions of communicating objects and classes that are customized to solve a general design problem in a particular context. Meaning, they are reusable, tried-and-true methods for overcoming programming problems that developers face time and again that allow them to solve the same sorts of problems in the same ways without having to constantly reinvent bespoke solutions.

In order to describe and evaluate when to apply a given pattern, I will be using the criteria that is given in the Design Patterns - Elements of Object-Oriented Software textbook:

A one to two word name that describes the solution.

This explains the specific problem that the design pattern is meant to resolve.

The solution is a high-level, conceptual description without implementation details.

Includes drawbacks for the design pattern, including reusability, coupling, and extensibility. This section should go into essentially when not to use a given pattern.