Standard Deduction subtracted before or after tax bracket calculated?

Are the Tax Brackets determined based on gross income (before the Standard Deduction) or the AGI (after the Standard Deduction ($25,100)?

 

The 2021 Tax Bracket of 12% for Married filing jointly is $19,901 to $81,050. So, as an example, with an income of $100,000 gross, the taxable income would be $74,900 and taxed at 12%. Is this correct?

Does SS income and an unemployment income effect the tax bracket or tax rate for that $74,900 AGI ?