Why is this code throwing an error?

Question

Python

Hello, I am a beginner in programming. I would like to understand why in the first code it does not give an error, but in the second it does?

x = 50
def func(x):
    print('x равен', x)
    x = 2
    print('замена локального x на', x)
func(x)
print('x по прежнему', x)

second code

x = 50
def func():
    print('x равен', x)
    x = 2
    print('замена локального x на', x)
func()
print('x по прежнему', x)