What does an ampersand (&) mean in the Swift language?

Question

I know about the ampersand as a bit operation but sometimes I see it in front of variable names. What does putting an & in front of variables do?

Answer 1

It means that it is an in-out variable. You can do something directly with that variable. It is passed by address, not as a copy.

For example:

var temp = 10
func add(inout a: Int){
    a++
}
add(inout:&temp)
temp // 11