the standard deduction is a fixed amount based on filing status and if over 65 there is an additional amount. itemized includes medical expenses in excess of 10% of adjusted gross income, taxes up to $10,000, charitable contributions, home mortgage interest subject to certain limitations, investment interest expense limited to investment income.
if itemized deductions are entered TT compares that to your standard deduction and takes the larger.
for 2019 standard is single 12200 double that for a joint return addition 1300 if over 65 double that if joint return and both over 65
