What are optionals in Swift?

Optionals are one of Swift's most important features — they represent a value that may or may not be present. A variable of type String? can contain either a String or nil. This forces explicit handling of the absence case, preventing null pointer crashes. Declaring optionals: var name: String? = "Alice" var age: Int? = nil // No value. Unwrapping optionals: (1) Optional binding (if let): safest — if let unwrapped = name { print("Name: \(unwrapped)") } else { print("No name") }; (2) guard let: early return pattern — guard let name = name else { return } // name is non-optional from here; (3) Nil coalescing (??): provide default — let displayName = name ?? "Anonymous"; (4) Optional chaining (?.): access properties/methods that may fail gracefully — let count = name?.count // Returns Int?; (5) Force unwrap (!): dangerous — crashes if nil — let forced = name! // Only if 100% sure it's non-nil. Implicitly unwrapped optionals (!): var label: UILabel! — declared as optional but used as non-optional. Used for properties that are set after init (IBOutlets). Optional map/flatMap: let uppercased = name.map { $0.uppercased() } // "ALICE" or nil.