Please see the following links.
TurboTax Free File Program is geared towards lower-income filers, regardless of tax return complexity, and is only offered through the IRS Free File Alliance (FFA) program. No upgrades are available.
TurboTax Free Edition, on the other hand, can be used by higher-income filers but only handles simple returns with no additional schedules. Upgrades and add-ons, such as TurboTax PLUS and Audit Defense, are available.