Hi @HENRY_CHAI ,
You can use an Attended or a UnAttended bot program without the Orchestrator, but if you want to control multiple UiPath Robots in executing repetitive business processes you have to use the Orchestrator.
Orchestrator lets you manage the creation, monitoring, and deployment of resources in your environment.
It acts as an integration point with third-party solutions and applications.
Its power comes from its capability of managing your entire Robot fleet.
For more details, you can check this topic
On their workstations, you need to install UiPath Robot Only - Recommended if you only need to execute automation projects on that machine