Progressive Taxation
The US uses a progressive tax system. Your income is not all taxed at the same rate. Instead, each portion of your income is taxed at the rate for the bracket it falls into.
Effective vs Marginal Rate
Your marginal rate is the rate on your last dollar earned (the highest bracket you reach). Your effective rate is the average rate across all your income — it is always lower than the marginal rate because lower brackets are taxed at lower rates.
Standard Deduction
The standard deduction reduces your taxable income before brackets are applied. For 2024, the standard deduction is $14,600 (Single), $29,200 (Married Filing Jointly), or $21,900 (Head of Household).