The program is a partnership between the IRS and popular tax filing software's like TurboTax, TaxSlayer, TaxAct, etc... that allows you to file your entire return for free if you make less than the $72,000 AGI cutoff.
Here's the link to IRS Free File
Even if you do make more than $72,000/year the electronic forms to file are free to use and file online. Granted I would only do that if you have a pretty straightforward tax return or you really know what you're doing when it comes to taxes.
If you're unsure of what steps to take, here is a guide walking you through the free file program.