The standard deduction is a dollar amount that reduces the amount of income on which you are taxed and varies according to your filing status; there is also an additional standard deduction for individuals who are blind or age 65 or over.
You CANNOT take the standard deduction if you itemize deductions. In addition, certain individuals cannot take a standard deduction or can take only a reduced standard deduction.
Publication 17, Your Federal Income Tax - Chapter 20, Standard Deduction - Essential guidance
Publication 501, Exemptions, Standard Deduction, and Filing Information - See Standard Deduction for detailed guidance