I want to understand the swift code before I learn it. I understand it

/// - Note: Type Constraints in Action
func findIndex(ofString valueToFind: String, in array:
               [String]) -> Int? {
    for (index, value) in array.enumerated() {
        if value == valueToFind {
            return index
        }
    }
    return nil
}
let anotherStrings = ["cat", "dog", "llama", "parakeet", "terrapin"]
if let foundIndex = findIndex(ofString: "llama", in: anotherStrings) {
    print("The index of llama is \(foundIndex)")
}
/// - Note: Type Constraints in Action (Generic Way)
func findIndex<T: Equatable>(of valueToFind: T, in // must be Equatable
                             array:[T]) -> Int? {
    for (index, value) in array.enumerated() {
        if value == valueToFind {   // not every type is equatable
            return index
        }
    }
    return nil
}