iOS 中的像素和点是什么

Swift
import UIKit
class ViewController: UIViewController {
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let label = UILabel(frame: CGRect(x: 20, y: 50, width: 200, height: 30))
        label.text = "Hello, World!"
        label.textAlignment = .center
        self.view.addSubview(label)
        
        let button = UIButton(frame: CGRect(x: 100, y: 100, width: 100, height: 50))
        button.setTitle("Click Me", for: .normal)
        button.backgroundColor = .blue
        button.addTarget(self, action: #selector(buttonClicked), for: .touchUpInside)
        self.view.addSubview(button)
    }
    
    @objc func buttonClicked() {
        print("Button Clicked")
    }
}