Tax bracket
A range of income taxed at a certain rate. US federal income tax has 7 brackets, from 10% to 37%.
Each bracket applies only to the slice of income that falls inside it. Moving into a higher bracket does not raise the tax on the income below it.
The income ranges for each bracket change every year with inflation and depend on your filing status. The IRS publishes the current ranges. Brackets apply to taxable income, which is your income after deductions like the standard deduction.