Confusion @gst

1) Section 17(5)  of  the CGST  act  2017  is define  block credit  (No ITC available )  on  Goods and services  or both .

2) exempt supply define under  section  2(46)  of the CGST  act  2017  - means supply of any goods or  services or both which attracts  nil rate of Tax or which may be wholly exempt  form Tax under section 11 of  the CGST act 2017 or under 6 of the IGST   act 2017 and includes non--taxable supply 

3) No Definition  of Specific GST  under  GST  law  or  please elaborate this query

4) No Definition  of common GST  under  law  but in general   taxable supply of all goods and services  which attracts  GST ,   at proscribe  rate  under  Law   . 

PLEASE GUIDE ME ABOUT GST ON WORKS CONTRACT.

I AM IN CONFUSION