Your "gross income" is all the money you've earned in wages or salary, received as interest, gifts and prizes. Basically, anything you got in some form of cash. (It doesn't include things like increases in the value of property, or stock options.)

For tax purposes, you are allowed to deduct a standard amount of money for personal living expenses, some kinds of interest, and some other expenses. After subtracting these from your gross income, the result is your adjusted gross income or AGI.

You pay taxes on your adjusted gross income. This value is used to calculate how much you owe in taxes.

After calculating your AGI, you can take additional itemized deductions.

To qualify for Free File, your AGI must be less than some set amount (in 2009, it was $57,000). Because your AGI is calculated by subtracting some deductions, like mortgage interest, your gross income could be substantially higher than the maximum. If your gross income was less than $70,000, you are probably eligible to use Free File.