No. The value of employer-paid health insurance for an employee, spouse, and dependent is a tax-free fringe benefit. However, under the Affordable Care Act, employers (other than small employers currently exempt from this obligation) must report health insurance on W-2s. Presumably, this information is being used by the government for rules in the future; there is no current or future rule on the books that taxes this fringe benefit.
Gross income less allowable adjustments, such as IRA, alimony, and Keogh deductions. AGI determines whether various tax benefits are phased out, such as personal exemptions, itemized deductions, and the rental loss allowance and modified adjusted gross income (MAGI).