Hello,Tyrannosaurusss ;) Which of these words you can use, has mainly determined by the gender of a noun. "Он" always refers to some man ,a male animal or a masculine noun. Some example: a)Он всегда выглядит опрятным и ухоженным.(a man) b)Он не кусается.(When you taking about your lovely dog,for instance) c)Этот булыжник очень большой.Да он просто огромен!(The 'cobblestone' has masculine properties as a noun in Russian). "Она" is just opposite and refers to woman ,a female animal or a feminine noun. a)Она как всегда выше всяких похвал. b)Она очень игрива.(She is very playful(a pussycat)). When you refer to group of people (or a bunch of animals,plants etc.),regardless of their gender/sex,you can say "oни". a)Они решили отдохнуть в конце рабочего дня.(people) b)Они просто чудо!(flowers). "Oно" is neuter and refers often to an inanimated object in a neuter form. a)оно дырявое.(the bucket) b)Дерево сохнет. Оно уже очень старое.('The tree' is a neuter noun in Russian.)

you can use example :she go - она идет, he go - он идет, they go - они идут,it go - оно идет;atau big sentence:she now in home - она сейчас(now) дома(home,but *The Nominative case дом or not дома ),or he go to home - он идет(go) домой(home)

you are pop with your friends...

Please be kindly advised that you have mistakenly flipped around the "language of learning" and the "language of use". Hence, for this question, you should have placed "Russian" as the former one, and "English" as the latter one, in order to attract more Russian speaking members to read your post, and to answer your questions when available. I am sorry to say this, but your question is honestly involved of the most basic grammar structure in Russian. I believe that the reason why you were confused is mainly because you are not used to various genders (such as masculine, feminine and even neutral) in other foreign languages. Once you are well used of such gender variations, those third-person personal pronouns should not raise so much difficulty to your side. Take care and good day.

он - he она - she оно - it они - they