In Swift, the Nil Coalescing Operator (??) is used to provide a default value for an optional if the optional is nil. It's a shorthand way of handling optionals that allows you to provide a fallback value in case the optional is empty.

Here's the basic syntax of the Nil Coalescing Operator:

let result = optionalValue ?? defaultValue

optionalValue is the optional that you want to unwrap.
defaultValue is the value that will be used if optionalValue is nil.
The Nil Coalescing Operator returns the value of optionalValue if it's not nil, and defaultValue if optionalValue is nil.

Here's an example:

let userInput: String? = getUserInput() // This function returns an optional String
let username = userInput ?? "Guest" // If userInput is nil, "Guest" will be used as the default value

In this example, if userInput contains a non-nil value (e.g., "John"), the username constant will be assigned the value "John." If userInput is nil, username will be assigned the default value "Guest."

The Nil Coalescing Operator is a concise way to handle optionals and provide sensible default values when necessary, making your code more robust and readable.