Most cats despise and fear vacuum cleaners (so do most dogs) because of the noise they make. To the cat, the vacuum is like some noisy, threatening animal. But a few cat owners manage to get their cat comfortable with a vacuum cleaner, enough so that they can use a hose attachment and groom the cat.
This is amazing to watch, but if your cat will tolerate it, wonderful, for it is a tidy way to groom loose and dead hair off cats, especially longhaired ones. But don’t be surprised if your cat won’t cooperate.