SGST is one of the tax components of GST in India. SGST Act expands to State Goods and Service Tax.
It is one of the three categories under Goods and Service Tax (CGST, IGST and SGST) with a concept of one tax one nation. SGST falls under State Goods and Service Tax Act 2017.
A simple understanding could be that, when SGST is being introduced, the present state taxes of State Sales Tax, VAT, Luxury Tax, Entertainment tax (unless it is levied by the local bodies), Taxes on lottery, betting and gambling, Entry tax not in lieu of Octroi, State Cesses and Surcharges in so far as they relate to supply of goods and services etc. are subsumed into one tax in GST called State GST.
All the tax proceeds collected under the head SGST is for State Government.