Taxable income includes salaries or other employment income, interest and dividends, and long- and short-term capital gains and losses, and other sources of income.
The adjustments include certain IRA deductions, moving expenses, and unreimbursed business expenses. Here is a full list of Above-the-Line Deductions used in calculating AGI.
Adjusted Gross Income is figured on the first page of the U.S. federal tax return, and serves as the basis for the income tax you owe. If you're doing your own taxes, use tax software to automatically calculate AGI and to accurately do other tax calculations as the software walks you through the tax interview.