Hey,

In Category option UR means Unreserved or simply the general category. This category doesn't get any reservation in government job or educational institutions.

If you did not get  NCL certificate then you fall under Creamy layer and cannot enjoy reservations in government sectors. Therefore while filling up the form you need to choose UR as your category because during entrance exams or counselling you are supposed to carry your caste certificate,in case of failure you may become ineligible for admission.