CrewAI Tasks are the operational units within a multi-agent system, representing specific assignments for an agent to complete. Each task is meticulously defined with a description outlining the agent's objective and an expected_output specifying the desired format and content of the result. Workflow orchestration, in this context, is the systematic arrangement and management of these tasks, dictating their execution order (sequential, parallel, hierarchical), information dependencies, and the flow of control among multiple agents to achieve a larger, complex objective efficiently and reliably.