We have this code for the flag game project:

func askQuestion() {
      button1.setImage(UIImage(named: countries[0]), for: .normal)
      button2.setImage(UIImage(named: countries[1]), for: .normal)
      button3.setImage(UIImage(named: countries[2]), for: .normal)
  }

My confusion is this: according to the code, it seems button1 is "setting its image" to the output of UIImage's "named: countries[0]"

However, countries[0] is simply a string. How is the system getting an image out of it? Is it checking the assets for an image whose title matches the string in countries[0]?

Additionally, if I added a random string into countries like "Zebras", would UIImage be able to pull an image out of it as well even though it doesn't exist?

Trying to get a conceptual grasp of this code...

How is the system getting an image out of it? Is it checking the assets for an image whose title matches the string in countries[0]?

Yep.

Additionally, if I added a random string into countries like "Zebras", would UIImage be able to pull an image out of it as well even though it doesn't exist?

Nope. How would the system create an image if it doesn't exist in your assets?