In Swift an Optional Type is considered a safe way to use variables. An Optional can represent a value that has been set or more importantly the lack of a set value as they default to nil when no value is present (yes that technically means they do always have a value). You tell Swift that you want to use an optional type by using ? after the variable type, so for example.
var myOptionalVariable: Int?
// the value of myOptionalVariable is initialized to nil