UIPath Orchestration - Individual Robots Running on Separate Systems?

Regarding orchestrating multiple jobs across several robots:

  1. Are these robots on separate systems that I own or is it cloud based solution?
  2. If these are systems I own, do they have to be running and dormant so no one else can use the system while the job runs?
  3. What are the pros and cons of running robots on multiple systems vs. setting up a single system to run multiple robots? So in other words: Why do I need a cloud if I can just set up and schedule a single system to run all of the jobs for me?