An orchestrator is the central coordinator in a multi-agent or multi-step system. It decides which agents to invoke, in what order, with what inputs, and how to handle their outputs — including merging results, resolving conflicts, and recovering from failures. Orchestrators range from simple sequential pipelines to dynamic DAG executors that adapt their plan based on intermediate results. The orchestrator's logic is distinct from the agents it manages; it owns the workflow topology while agents own task execution.