what is mean of if __name__ == '__main__': code example

Example: if __name__ == '__main__': main()

print("before import")
def functionA():
    print("Function A")
def functionB():
    print(("Function B"))
print("before __name__")
if __name__ == '__main__':
    functionA()
    functionB()
print("after __name__")
#===Output===
#before import
#before __name__ guard
#Function A
#Function B
#after __name__ guard