I got a 3 month male kitten and recently stray cats have started to come to the house and started making weird noises that make my kitten terrified. What does this mean and what can i do about it
I agree with @kittyconsultant that if your cat isn't neutered they may be displaying for its benefit. Or, more likely, for the benefit of a nearby queen. If so, this will probably stop fairly soon, though it may happen again.
You have no control over the other cats. Your cat will learn that they can't get in and will not be terrified (though he may be either pleased by the fact that you help defend his territory, or frustrated that he can't get out to chase girls himself, again depending on whether he has been fixed.) Either way, it's really a problem that solves itself as he grows up.
Your kitten is just getting to the age that hormones are starting. Per our post What is most appropriate age to neuter/spay a cat? you should be scheduling an appointment to have your kitten neutered soon. This will keep him from being seen as threat by the local tomcats and help keep him safe.
Cats are very territorial. The outdoor cat may consider your house to be its territory. Thus your kitten is in its Territory. Cats spit and hiss and chase and attack other cats that they are not friendly with, that are in their territory.
The easiest thing is to cover the lower parts of your windows so the outdoor cat cant see the indoor kitten. If you have modern windows they cant really smell each other though them.
Out of sight, out of mind, problem solved.
I have used various craft and foam boards for this. Something the indoor cat can't remove. If you live someplace where your neighbors will not object to the eyesore you could prop up something against the window(s) from the outside. Whatever blocks the line of sight between cats.