Everyone gets to take a Standard Deduction amount off their income before the tax is calculated (it's a good thing - it lowers your income). Which means the first 12,400 Single (24,800 Joint) of your income is not taxed and is tax free. Unless their itemized deductions are more. Itemized deductions are things like Medical, Gifts to Charity, State Income Taxes Paid, Mortgage Interest, Property Taxes, Car Registration fees, etc.
For 2020 the standard deduction amounts are:
Single 12,400 + 1,650 for 65 and over or blind (14,050)
HOH 18,650 + 1,650 for 65 and over or blind
Joint 24,800 + 1,300 for each 65 and over or blind
Married filing Separate 12,400 + 1,300 for 65 and over or blind
See Tables 6 & 7 Standard Deduction Chart for Most People on page 24
https://www.irs.gov/pub/irs-pdf/p501.pdf
If you are a dependent your Standard Deduction can be less.
