You assigned the number 5 to the variable x. But then you told Python to print y — and nowhere in your code has y ever been given a value. Python’s error message:

NameError: name 'y' is not defined

is its way of saying “I’ve never heard of y.”

To fix it, you need to make sure you print the same variable you defined:

x = 5
print(x)   # prints 5

Think of variables like labels on boxes. You wrote the number 5 on a sticky note labeled “x” and stuck it on a box. Then you asked Python, “What’s in the box called y?” But there is no box labeled y, so it complained. The cure is simply: use the same label consistently.

If you want both x and y to exist, you’d have to assign both:

x = 5
y = 5
print(y)   # also prints 5