Regular Tax
If you don't have net capital gain income, the "regular tax" is what you get if you apply the regular tax rates to your taxable income and filing status.

If you have net capital gain income, the "regular tax" is the sum of the capital gains tax on your net capital income and the regular tax on your remaining taxable income.

Your "regular tax" is not the same thing as your tax liability. We may need to add additional taxes such as the alternative minimum tax and self-employment tax, or we may be able to decrease your tax with credits such as the child tax credit and the education credit.