The standard deduction is a fixed dollar amount that reduces the income you're taxed on, available to filers who don't itemize. For 2026 it's $16,100 for single filers and $32,200 for married couples filing jointly.
You take whichever is larger: the standard deduction or your total itemized deductions. The vast majority of filers take the standard deduction because it exceeds what they could itemize.