Fitting means that something can take up all space in an area it is in
Sealing means an area has no places anything in it can exit through
You're right, they're different things
UPDATE:; JUST GOT INTO AN ARGUMENT WHIT MY MOM BECAUSE I SAID SHE WAS REFERRING TO "SEALING" AND "FITTING" AS DIFFERENT THINGS, SHE SAID SHE WASNT, I SAID SHE DID NOW SHE'S PISSED AND WONT TALK TO ME. PLZ HELP. (THIS WAS ABOUT A PRESSURE COOKER AND IM NOT BACKING DOWN)