It has two meanings. On a payslip, it is what comes out of your pay: insurance and tax. In income tax, it is what lowers your taxable income: dependents, insurance, medical bills.
On your payslip and on the year-end adjustment forms.
On the payslip, check every line. For tax, every deduction you declare lowers the amount you pay.
General explanation, for guidance. Rules and amounts change: confirm with the responsible office.