The 1040 form was revised in 2018. It is now a shorter form and much of the additional information that would be reported on it has been moved to six different schedules. (The 1040A and 1040EZ forms no longer exist.)
Schedule 1, as is noted in the title of it, is where additional income and adjustments to income are reported in detail and then summarized on your 1040 form. The additional income reported on Schedule 1 is for capital gains, unemployment compensation, prizes/awards, or gambling winnings. The adjustments to income on Schedule 1 are for student loan interest, self-employment taxes, educator expenses, self-employed retirement or health insurance deductions, and IRA deductions.
Here is a link to the copy of the Schedule 1 form: IRS 2018 Schedule 1 Form