Game Loop:

Next, you need to add a "game loop"

Pygame requires a “game loop” that constantly redraws the screen.
What is a "Game Loop":
The entire game runs on one loop, which handles the updating and rendering of content; constantly looping through the game codes.
It's a loop because the game keeps doing a series of actions over and over again until the user quits.

Let's improve our current Python code by adding a game loop. Add the following code:

The game loop is a "while" loop that keeps going as long as the variable run is true.
Inside the loop, we start with the pygame.time.delay(100) which delays (pauses) the program for 100 milliseconds.
This determines how fast a character moves on screen when you press the keyboard keys
Then we have a for loop to constantly check if the user has closed the game window. When the user clicks on the X button (top right corner of the game window) to close the game, that's when pygame ends the game.
Lastly, the pygame.quit() methods that close the game window

Intro to Pygame - Cube Game Part 1