The Russian word этот is a demonstrative adjective that can be translated as this/that/these/those, depending on the context. (For a discussion of the this/that distinction, see the entry on тот.) It declines like this:
For first- and second-year Russian students, I call this word ‘changing это’ because it changes it's ending for case, number and gender. Beginners often confuse it with ‘unchanging это’; for discussion of the distinction, see this blog entry.
|— Что ты читаешь?
— Анну Каренину.
— Ох, как я люблю эту книгу!
|“What are you reading?”
“Oh, I love that book so much!”
|— Кто живёт в этом доме?
— Откуда мне знать?
|“Who lives in that house?”
“How should I know?”
|Эти упражнения очень трудные.||These exercises are really difficult.|
|Ты давно работаешь с этими людьми?||Have you been working with these people for a long time?|
Они is a pronoun that replaces grammatically plural nouns. It declines like this:
The primary meaning of они is they/them in its various forms. In such contexts you get sentences like:
|Они приезжали ко мне в воскресенье.||They came to my place on Sunday.|
|Я с ними познакомился в средней школе.||I met them in high school.|
|Откуда ты их знаешь?||How do you know them?|
|Как часто ты ходишь к ним?||How often do you go to their place?|
But the interesting part of this word is when it refers to plurale tantum nouns. Such nouns are ones that grammatically occur in the plural only, never in the singular. Sometimes a noun is plurale tantum in both Russian and English, like брюки pants. If они is referring to such a word, then its forms are simply translated as they/them:
|— Где мои брюки? Я их не вижу.
— Они на кухне.
|“Where are my pants? I don't see them.”
“They're in the kitchen.”
Sometimes a noun is plurale tantum in Russian, but singulare tantum (singular only) in English, such as деньги money. When они refers to such a word, then its forms are simply translated as it:
|— Где мои деньги? Я их не вижу.
— Они на столе.
|“Where is my money? I don't see it.”
“It's on the table.”
The word мы means we. It declines like this:
I often encounter the word in sentences like this:
|Мы купили пять aбиссинских кошек.||We bought five Abysinnian cats.|
|Нас выбросили за борт.||They threw us overboard.|
|Через неделю к нам приедут гости.||We have guests coming in a week.|
|Вы можете связаться с нами по этому телефону.||You can make contact with us at this number.|
|Мы взломали сейф и взяли бриллианты.||We broke into the safe and took the diamonds.|
The word она is a personal pronoun that declines like this:
The «н» versions of the pronoun occur when the pronoun is the object of a preposition.
Она refers to feminine singular nouns, which can be either people or things, so sometimes it is translated as she/her, and sometimes it is translated as it. In other words, if you are refering to an учительница "school teacher," then the sentence must be translated with she/her, and if you are refering to a машина car, the same sentence must be translated with it:
|Где она?||Where is she/it?|
|Я вижу её.||I see her/it.|
|Дети танцевали вокруг неё.||The children were dancing around her/it.|
|Мы поговорили о ней.||We had a chat about her/it.|
|Я подошёл к ней.||I walked up to her/it.|
|Перед ней стоял иностранец.||A foreigner stood in front of her/it.|
In casual conversation it's common in America to say things like “Me and Sally went to the store,” especially when we are children. Schoolteachers then try to beat us out of that habit and make us say “She and I went to the store.” Because of that influence, English speakers may be tempted to say things like «Она и я ездили в магазин» in Russian. While theoretically one can say that in Russian, no one ever does. Instead it gets rephrased as “we with her” «мы с ней». Of course, it would be ridiculous to translate that as “we with her” in English; you still want “she and I” or just plain old ‘we.’
|Мы с ней ходили в кино.||She and I went to the movies.|
|Мы с ней поспорили с вышибалой, и нас выгнали из клуба.||She and I argued with the bouncer, and they threw us out of the club.|
The Russian word for ‘what’ is что. Although it is written with the letter ч, the nominative/accusative form of the word is most commonly pronounced [што]; in the other cases we do pronounce ч as ч. It occurs in all six cases:
Notice that the only difference between the prepositional and instrumental forms is the двоеточие “double dots” over the prepositional form.¹ Remember that the Russians usually do not usually write the double dots, so context will have to tell you how to pronounce those forms. Some sample sentences:
|— Что ты купил?
— Овощи и чай.
|“What did you buy?”
“Vegetables and tea.”
|Что там лежит на столе?||What's that lying on the table?|
Somewhere in school every American is taught the rule “never end a sentence with a preposition.” For English it's an assinine rule that has no reasonable justification in the living language.² However, for Russian the rule is real and alive. It's not an artificial rule, as in English, but rather a subconscious part of the living language: no Russian will ever end a sentence with a preposition, not even accidentally. So whenever you are translating a question from English to Russian, and the question ends with a preposition, you need to move that preposition to before its object and then translate. Thus:
|— В чём живут пчёлы?
— В ульях.
|“What do bees live in?”
|— Из чего сделан тот сарай?
— Из досок дуба.
|“What's that shed made of?”
“It's made of oak boards.”
|— Чем ты написал сочениние?
— Тогда надо переписать ручкой, а то не примут.
|“What did you write your composition with?”
“With a pencil.”
“Then you'll have to rewrite it with a pen, otherwise they won't accept it.”
|— К чему стремятся глобалисты?
— К унифицированию всего человечества.
|“What are the Globalists striving for?”
“For the unification of all humanity.”
|— Мы встретились перед памятником Пушкину.
— Перед чем?
— Перед памятником Пушкину.
|“We met in front of Pushkin's monument.”
“In front of what?”
Notice in the last example we can leave the preposition out of the response in English, but in Russian you must retain the preposition to justify the case of памятник.
¹ The double dots symbol is often called a diaeresis or an umlaut. The former is theoretically used to indicate that a vowel is pronounced as a complete vowel (not a diphthong) when preceded by another vowel with which it might blend. The latter is theoretically used to indicate that vowel is fronted. Since neither of those instances prevails in the е/ё distinction, “double dots” is a sensible name for the symbol.
² Of course, one can't mention this rule of English without mentioning Winston Churchill's famous definition: “A preposition is a word you can't end a sentence with.” I actually doubt that Churchill said it, but it's too fun not to mention.