what are the main types of credit?

The answer to your question is already covered in our study material. Follow the given link and scroll down to the topic 'classification of rural credit' to view the same.

https://www.meritnation.com/cbse/class11-commerce/studymaterial/economics/indian-economic-development/unit-iiirural-development/442_2488_6390#slide1_Rural credit and its Sources