It's the line that shows the federal income tax that was withheld on your w-2 forms. When you enter in your W-2 forms this amount is listed in box 2. If you e-file this information is automatically sent to the IRS along with the copy of the W-2 that you input. However, when you paper file your tax return you must attach a copy of your W-2 forms. Please view a copy of form 1040-EZ at the link below.
https://www.irs.gov/pub/irs-prior/f1040ez--2016.pdf
