turtle.goto()

the turtle.goto() function tells the turtle to go to a certain place on the screen. type the x coordinate, than the y coordinate. When you run it the turtle will go to that place on a screen. If it doesn't work, you might be on a different version of python that doesn't support it.

turtle.ycor() and turtle.xcor()

the turtle.ycor() and turtle.xcor() functions can be used for many things. Like this:

if turtle.ycor() > 39 and turtle.ycor() < 34:
    print("Hello, World!")
else:
    print("Goodbye. World?")

this may not work on repl.it. Than there's the while True: function. You need to make sure you capitalize the True. This is a forever loop, because it is always true. If you want to make a loop until the user does something for example:

while a = 5:
    print("5")

Those are a few advanced things in python. There is probably a lot more, but you can learn those using the internet. Thankyou for reading this, and goodbye