A subJob is graphically defined by a blue square gathering all connected components that belong to this subJob. Each individual component can be considered as a subJob when they are not yet connected to one another.
This blue highlight helps you easily distinguish one subJob from another.
Note: A Job can be made of one single subJob. An orange square shows the prejob and postjob parts which are different types of subJobs. For more information about prejob and postjob, see Using the tPrejob and tPostjob components.