Let me just ask this…Did you run your process after deleting the robot or machine?
If your answer is no (you will not be able to) then that exactly answers your question.
Machine is whatever system/VM/server machine your robot service is installed in and provisioning is like connecting the robot to the said machine through the Orchestrator.
Robot can be created and provisioned to any machine through a common Orch.(means anyone can run a process in your machine if it is provisioned to the same)
You will know the process when it ran, where and its status (failure/successful) from the Jobs tab in your Orch. you can download the logs too.
They are definitely related. If machine key isn’t supplied in the robot tray then your Robot service is not connected to Orch. that means no process can be triggered from Orch, only from tray can you run a process which defeats the purpose of multiple bots.
Hope this clears up some doubts.
PS : And Bots should always belong to an environment.