Remind me: why do we use a \ on the 2nd line before number?

for number in 1...10 {
  println("\(number) * 7 = \(number * 7)")
  }

This example is the answer to the For-In Loop Challenge. Essentially the line of code (number) within the println statement is the same thing as saying " 1, 2, 3, 4, 5, 6, 7, 8, 9, 10" each at the beginning of a new line. Then by using (number * 7), you are saying "7, 14, 21, 28, 35," etc.." therefore making each new line read "1 * 7 = 7" , "2 * 7 = 14", "3 * 7 = 21", and so on until the numbers 1 through 10 inclusive have each been multiplied by 7 on a new line.

I was wondering about this as well and Kyle Vandeven's response above didn't convince me that the backslash in this case created a new line (which is what the println function does). You can test this by removing the backslash character in Kyle's example response to the For-In Loop Challenge:

for number in 1...10 {
    println("(number) * 7 = \(number*7)")
}

This results in:

(number) * 7 = 7 (number) * 7 = 14 (number) * 7 = 21 (number) * 7 = 28 (number) * 7 = 35 (number) * 7 = 42 (number) * 7 = 49 (number) * 7 = 56 (number) * 7 = 63 (number) * 7 = 70

The backslash is therefore required to pass the value of number to the println function.

Apple's documentation explains this a bit better:

https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/StringsAndCharacters.html#//apple_ref/doc/uid/TP40014097-CH7-ID292