'প্রোটোকল হল একটি ইন্টারফেস, যা কিছু properties এবং methods কে define করে।' The protocol is an interface that describes some properties and methods. Any type that conforms to a protocol should fill in the specific properties defined in the protocol with appropriate values and implement it's requisite methods. For instance: protocol Queue { var count: Int { get } mutating func push(_ element: Int) mutating func pop() -> Int }