The then field specifies a code pathway to execute if the condition in an if tag is met.
The else field specifies an alternative code pathway if the condition in an if tag is not met.
An if tag contains a condition in its primary field, an optional then field containing code to execute if the condition equates to true, and an optional else field containing code to execute if the condition equates to false.
If the code in the then or else field is executed, any values produced by the sequential execution of that code form the result produced by the if tag and are pushed out to the parent field of the if tag.