$iif(C,T,F)
Returns T or F depending on whether the evaluation of the Conditional C is true or false.
$iif(1 == 2, yes, no) returns "no"
$iif() returns F if the conditional returns zero, $false, or $null. For any other value $iif() returns T.
If you don't specify the F parameter, $iif returns a T value if the condition is true, and returns nothing if it's false.
$iif(1 == 2, yes) returns nothing
You can find out more about conditionals in the if-then-else section.