"Subject?" asks whether the person has been chosen as a Subject.
"Is Open?" asks whether the Questionnaire for that person is active i.e. available for responses. If not, the questionnaire has been closed for responses, probably by generating a Report. (Questionnaires show as Open even before the "Starting Date For Responses" set on the Project tab.)
"Self-Responds?", asks whether the Subject will be invited to respond to her/his own questionnaire. To respond is the default, indicated by a checkmark. If no checkmark, the person cannot respond to their self-assessment questionnaire.
"Self Response PID" is the PID used by the Subject to respond to her/his own questionnaire.
