What is the difference between "Inferred" and "Freeform" in Xcode Storyboard?

Inferred resizes the scene according to its parent scene. For example if you have a scene that is the size of an iPad and then you add a new scene to your storyboard and create a segue to it, it will automatically resize to the same size as the iPad scene (where the segue originates from).

Freeform ignores the above rule and you're able to size it as you see fit, in the utility pane on the right.

Both of these however have nothing to do with how the view is displayed and sized on actual devices. For that you need to use auto layout and constraints. Or springs and struts. Some even do it in code if they need more flexibility.

“Inferred” is the default setting for storyboards and it means the scene will show a navigation bar when it’s inside of a navigation controller, a tab bar when it’s inside of a tab bar controller, and so on. You could override these settings if you wanted to, but keep in mind they are here only to help you design your screens. The Simulated Metrics aren’t used during runtime, they’re just a visual design aid that shows what your screen will end up looking like.

"FreeForm" Usually you use the freeform property when you add the view controller as a child to another view controller programmatically and you really want to have that fixed size.If you push the view controller or you present it as modal view controller (and you use the modal presentation styles) then there is no need to use freeform.Also another use of the freeform property is to preview the actual size of your view controller when is presented as a modal view controller using existent presentation styles.