Is it necessary to create a structure that conforms to the protocol?

Yes, the structure can conform to the protocol.

protocol Greetable {
    func greet()
}

struct Person: Greetable {
    let name: String

    func greet() {
        print("Hello, my name is \(name).")
    }
}

Structures that conform to protocols allow the use of both value semantics (copying) and the abstraction provided by protocols.