TrueOrFalse Type

A TrueOrFalse Property, as the name implies, allows you to say whether something is true or false.

If you say that your Property is Optional TrueOrFalse, that essentially introduces the concept of "Maybe" -- a value that is neither True nor False.

TrueOrFalse values are called "Boolean" in most programming languages; we are deliberately avoiding that particular bit of computer-science jargon.