What does 'orchestration' refer to in the context of Docker?

In the context of Docker, 'orchestration' refers specifically to the automated management and deployment of containerized applications across multiple hosts. As applications evolve, especially in microservices architectures, the complexity of managing containers increases significantly. Orchestration tools help automate various tasks, including scaling, load balancing, service discovery, and fault tolerance, thereby simplifying the deployment of applications that may consist of numerous interconnected components.

Using orchestration, developers can define the desired state of their applications, and the orchestration tool ensures that the actual state aligns with this desired state. This capability is crucial in production environments where applications must be resilient and responsive to changing conditions.

The other options, while relevant to software development and Docker, do not capture the comprehensive functionalities associated with orchestration. For example, designing software architecture is a broader activity that does not specifically entail management of containers. Manual deployment contradicts the essence of orchestration, which emphasizes automation. Similarly, creating custom Docker images focuses on individual containers and their configurations rather than the holistic management of these containers across diverse environments.