Difference between Run, RunOnce, Active Setup and RunOnceEX

Run: Runs the command or code each time a user logs in the machine.

RunOnce: The command or code runs once for current logged in user and clears the registry key as soon as the command is run successfully.

RunOnceEx:  clears the registry key on completion of the command.

Active Setup: The Key runs once for each user in the machine.