What is the difference between wildlife sanctuary,national park and biosphere reserve ?

Biosphere reserves:  
The areas of ecosystem, which are protected by the national governments for the conservation of biodiversity (flora and fauna as well as human communities inhabiting in that region) with its sustainable use, are called biosphere reserves. Conservation of landscapes, ecosystems,
species and genetic variation as well as economic and human development are included in the functions of biosphere reserves. Apart from that, these reserves are used to support research, education and information exchange too.

National Park:  
The protected areas which have one or more ecosystems including natural landscapes and a great natural beauty. The plants, animal species, geomorphological sites and habitants of the region are protected by the government. Also, these areas are used to promote scientific research and education.

Wildlife sanctuary:

Wildlife sanctuaries are the places where the wild animals are protected and provided with all of the required facilities to live comfortably and safely till they die naturally.