what does raise exception do in python code example

Example 1: throwing an exception python

raise Exception("message")

Example 2: python raise exception

# this raises a "NameError"

>>> raise NameError('HiThere')

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: HiThere

Example 3: python: raise error

class MyError(TypeError):
    pass

raise MyError('An error happened')