OPT means 'Optional Practical Training' and allows the F-1 visa holders to work in the US for 12 to 24 months.
CPT means 'Curricular Practical Training' and allows the F-1 visa holders to work for up to 20 hours a week in a field related to their major, while engaging in studies.
Be advised that the AT (Academic Training) for the J visa holders is not the same as OPT/CPT and if you are on an AT you must check 'NO' on that question.