What is the difference between ViewController and UiViewController

I am trying to understand what is the difference between these two concepts.

When I speak about a controller in main.storyboard, do I mean UiViewController or ViewController? are they the same or complementary?

I tried to find some information but got mixed results, I would like you to explain it to me

UIViewController is a class in the UIKit framework. Thing that controls a UIView (aka "view controllers") inherit from UIViewController.

If you create a new iOS app project in Xcode, and choose to use UIKit as the UI framework, it will generate a class called ViewController as part of the project template.

class ViewController: UIViewController {
    ...
}

This ViewController is a view controller, so it inherits from UIViewController. Note that ViewController is just a random name for the view controller that Xcode chose, it could just as well be YourAppViewController or even FooBarBaz.

You can also find view controllers in the storyboard. Those are the yellow circles with a white square inside. If you have just created a new project, the only one there would be the ViewController Xcode generated. You can see which view controller class a view controller in the storyboard corresponds to by selecting it and checking the "Class" field in the identity inspector:

That iPhone-looking part is the UIView that it controls.