Deductions such as medical expenses, charitable contributions, mortgage interest, property taxes, state and local income or sales taxes and others are what is known as “itemized deductions”.  You can see a more complete list of all these deductions, at least the most common, by looking at Schedule A of Form 1040.  They are used to reduce your taxable income.  The total of all your itemized deductions must exceed your standard deduction to be of any tax benefit.  Anyone filing a Federal income tax return (other than children under the age of 24 with unearned income) is entitled to the standard deduction.  The standard deduction for 2016 is $6,300 Single and $12,600 Married Filing Jointly.