Diffrence between taxes

Nil Rate
This type of supply attracts a GST of 0%. Input tax credit cannot be claimed on such supplies. Some items which are nil rated include grains, salt, jaggery, etc.

Exempted
This supply includes items which are used for everyday purposes. Since they are basic essentials, they do not attract any GST at all. You will not be able to claim any ITC on such supplies. Some examples are, bread, fresh fruits, milk, curd, etc.

Exempt Tax

Exempt U/S 11cgst &, U/S 6 igst says: government has power to notify in public interest any goods and services to exempt or nil rate by issuing of notification.
Hence on any exempted supply the tax is exempted (Not Nil)

Zero Rated
As per section 16 IGST : Zero rated supply is export of Goods & Services .

Not Taxable :
can be Non GST supply ie alcoholic liquor for Human consumption (As per sec.9)
can be exempted supply

Taxable :
taxable supply on which GST is applicable