A security token in authentication is used to verify the identity of a user. It typically contains information such as user credentials or a reference to the user's identity stored on a secure server, ensuring secure access to resources.

The Observer design pattern defines a one-to-many dependency between objects. When the state of one object changes, all its dependents (observers) are notified and updated automatically.

Agile is a software development approach that emphasizes iterative development and the delivery of working software in short, incremental cycles. It focuses on collaboration, customer feedback, and adaptability to changes throughout the development process.

The Facade Pattern is a design pattern in OOP where a single class (the facade) provides a simplified interface to a set of interfaces in a subsystem, making it easier to use and reducing dependencies.

In Test-Driven Development (TDD), failing tests are written first to initially fail. This establishes a clear criterion for success and guides the subsequent development process. Developers then write code to make the failing test pass, adhering to the test cases they've defined.

The Singleton design pattern ensures that a class has only one instance and provides a global point of access to it. This is particularly useful when exactly one object is needed to coordinate actions across the system.

The purpose of logging in software development is to record and analyze program behavior. It helps developers understand how their code is behaving in different scenarios.

The method used to traverse a graph or tree data structure is Depth-First Search (DFS). It explores as far as possible along each branch before backtracking.

In the context of responsive design, CSS stands for Cascading Style Sheets. CSS is used to control the presentation and layout of web pages, playing a crucial role in creating responsive designs.

The command used to clone a repository from a remote server to your local machine is git clone. This command creates a copy of the repository on your local system, allowing you to work on the codebase.

To reduce load times for international audiences, edge caching with CDN nodes strategically placed globally is effective. It ensures that content is served from a server closer to the user, minimizing latency.

Polymorphism in OOP refers to the ability of a class to provide different implementations for the same method. For example, method overloading and method overriding are forms of polymorphism. Method overloading involves defining multiple methods with the same name but different parameters in the same class. Method overriding occurs when a derived class provides a specific implementation for a method already defined in its base class. This flexibility allows for more versatile and readable code.