You do not get paid for NITI Aayog internships as they hire interns on unpaid basis. The main purpose for the internships is to provide industry exposure to the students.
Once you are hired, you will closely work with various departments as per your field and their requirements. This will help you in building various skills like communication, networking, research, presentation, etc.
As per my research, NITI Aayog internships are unpaid and you only get a certification of completion at the end. But, you will learn a lot and it will be a great experience for freshers to work closely with government departments and on projects that might be directly impacting the people of India. So, if you have some spare time and want to build some good skills then do apply for NITI Aayog internships and hope to get selected.