difference between 0 rated and exempted

For zero rated goods, you can claim a tax credit since the rate exists even if it is zero. This is generally done for necessities by the govt to lower their prices. For exempted goods, however, you can't take any tax credits. Look at it this way, for zero rated goods, you are paying tax @ 0%. On the other hand, for exempted you aren't taxed AT ALL .

Pranjali kya khoobh kh gayi very very gud answer

Zero rated is defined in IGST Act where any goods or services are exported out of India or supplied to SEZ

Whereas exempted goods are those which by virtue of section 11 of CGST Act are exempted from GST by order of the government.

Also regarding credits our professional colleague Ms. Pranjali has given suitable explanation.