OPD stands for Out Patient Department.
This is where one consults a doctor according to their issues.
Out patient means patients who are not admitted to the hospital. These are basically synonymous to doctor’s chambers. It is the same as taking an appointment and visiting a doctor’s chamber, just here, the “chambers” are under the hospital’s banner and one takes the appointment, on reaching the hospital, from the reception, whereas you might have to take prior appointment while visiting a doctor in a chamber.
The hospital’s doctors have a particular schedule as to who sits in the OPD on which day, one will have to consult the the doctor in charge on the day of the visit. For example, if you’re having chest pain, you will be asked to consult the doctor in the cardiology OPD. Whereas, in a private chamber scenario, when you have chest pain, you choose which particular doctor’s chamber you want to visit.