If you spend time stroking your cat, you probably have experienced her sticking her butt in the air and raising her tail, when you have been stroking her for a while.
It is also quite likely that she will position herself so that her backside is facing you.
This means that you get a full view of the wrong end of your cat.
You may not think that your cat's rear end is the nicest thing to look at and you may think your cat is being offensive when she does this.
But there is no insult meant by this at all.
Your cat is in fact, showing you a lot of trust. After all, she would not make herself vulnerable like that if she did not have complete trust and faith in you.
From the moment of birth, a mom cat tends to the cleaning of her precious kittens.
She uses her tongue to clean them all over, including their genitals and anus. This action is instinctive and it's very important. The new kittens cannot clean themselves and lack of hygiene would mean big problems.
There is also another reason that the mother cat licks her kittens' anus.
Kittens are born in to this world pretty much helpless. They cannot hear, they cannot see and they don't have the motor skills to move about.
Another thing they cannot do is pee and poop without mom helping them. She does this by licking their genital regions and anal areas to stimulate them into eliminating.
What has all this to do with your cat raising her butt in the air when you stroke her?
Your cat looks upon you as a mother substitute. Of course she knows that you are not a cat, let alone her mom, but you have taken her mother's place in many ways.
You feed her and take care of her. When you stroke her it is very reminiscent of her mom licking her to clean her up, a good memory.
When mom licked her clean, she always attended to her rear end.
So when you stroke her, her tail goes up out of the way and her butt is lifted for you to clean! Well, your cat does not really anticipate that happening, the response is automatic.
That is one theory as to why your cat raises up her butt when your stroke her. There is another theory.
When two cats meet who are on friendly terms with each other they often perform a little ritual of greeting.
They start by rubbing their cheeks against each other, this releases pheromones that signals to the other cat that everything is cool. They then move on to rubbing themselves against the other cat's body, this reinforces the greeting.
Finally one cat will raise up it's tail and offer it's butt to be sniffed. Yes indeed, gross for us humans, but only politeness for cats.
And that's the other theory. When your cat raises up her butt when you stroke her, she is inviting you to . . . well, she is only being polite.
It doesn't matter for what reason your cat's derrière goes up in the air when you stroke her, she doesn't expect you to do anything about it.
You can be assured though that she does not mean any insult by it, in fact she is paying you quite a compliment, it's a cat thing.