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

If you put & before a variable in a function, that means this variable is inout variable.

@Icaro already described what it means, I will just give an example to illustrate the difference between inout variables and in variables:

func majec(inout xValue:Int, var yValue:Int) {
    xValue = 100
    yValue = 200
}

var xValue = 33
var yValue = 33
majec(&xValue, yValue: yValue)
xValue //100
yValue //33