When you pay the fees offline then yes you get three different slips. The bank copy is being kept by the bank as proof that you have paid the fees. The ruhs copy is to be deposited in the college as a proof that you have paid the college fees. The candidate copy will remain with you so that you can show that you have paid the fees 

The ruhs copy need to be submitted in the college at the time the college start so that you can get proper enrollment in the college