TDS = Tax deduction at Source , it i s usually defined by Income tax deduction at source but it is not complete definition of income tax, TDS is applicable under GST rules also,
Income Tax deduction is also termed as TDS,
TDS can be set off against the total tax liability of the person while filing returns, if the tax liability is NIL at the time of filing returns, the the whole TDS deducted would be subject to refund.