difference between != and is not

[akbarza]

hi
I wrote the below code in vs code and it took an error in line 7 but in idle the code ran okay:

 '''a test for regex
'''

import re
REGEX = r"(?im:foo),\w+"
m = re.search(REGEX, 'FOo,bar_baz')
if m is not None: # i first had written m != None,
    # Comparison 'm != None' should be 'm is not None'
    print(f'm.group(0): {m.group(0)}')
else:
    print(f'result of match is: {m}')

in line 7 as you can see, I first wrote

 m!==None

and vs code took an error and suggested to me
to change to

 m is not None

.
what is the difference between !== and is not?
thanks