What does the subscript method in a Set collection mean and how is it used?

In Swift, the subscript method for the Set collection allows access to an element equivalent to the given key, or to add/remove an element. Unlike an array, where subscript works by index, in Set subscript is used to check for the presence of an element and to replace it.

Example usage:

var fruits: Set = ["apple", "banana", "orange"]

// Check for the presence of an element
if fruits["banana"] != nil {
    print("Banana is in the set")
}

// Add an element
fruits["grape"] = ()  // adds "grape"

// Remove an element
fruits["apple"] = nil  // removes "apple"

Thus, subscript in Set allows convenient working with elements by value, not by index.