У белой лошади красивая грива, а её копыта после дождя были мокрыми.

Russian very often expresses possession with the pattern:

• у + possessor in the genitive + possessed thing

So У белой лошади красивая грива literally means something like At the white horse, there is a beautiful mane.

This is the normal, natural way to say The white horse has a beautiful mane in Russian.

Russian does have иметь (to have), but it is used much less often than English have. In everyday Russian, the у + genitive pattern is usually preferred for simple possession.

Because the preposition у requires the genitive case.

Here the possessor is белая лошадь (white horse). In the sentence, it changes to genitive:

• белая лошадь → nominative
• у белой лошади → genitive after у

The adjective has to agree with the noun, so both words change:

• белая → белой
• лошадь → лошади

So у белой лошади means of the white horse / at the white horse.

In this possession pattern, the thing being possessed is normally in the nominative case.

So in:

• У белой лошади красивая грива

the possessor is у белой лошади, and the thing possessed is красивая грива.

That is why грива stays nominative, and the adjective agrees with it:

• грива is feminine singular
• so the adjective is красивая

This is different from English, where horse is the subject of has. In Russian, the possessed thing often behaves more like the grammatical subject.

А often means and, but not exactly in the same way as и.

Here а introduces the second part of the sentence and creates a slight contrast or shift of focus:

• У белой лошади красивая грива, а её копыта после дождя были мокрыми.

It is like saying:

• The white horse has a beautiful mane, and as for its hooves, they were wet after the rain.

So а is very natural here because the speaker moves from one feature of the horse to another.

If you used и, it would sound more like simple addition with less contrast or topic shift.

Also, Russian puts a comma before а when it joins two clauses like this.

Here её means her or its in the possessive sense:

• её копыта = her hooves / its hooves

In modern Russian, the possessive forms:

• его = his/its
• её = her/its
• их = their

do not change for case, number, or gender when they are used as possessive words.

So you get:

• её грива
• её копыта
• её ноги

The form stays её every time.

That is important because the same written form её can also be the object pronoun her, but here it is clearly possessive because it comes before a noun: её копыта.

Yes, that is possible.

Russian often omits possessive words when the owner is already obvious from context. So after mentioning the horse, a speaker could say:

• У белой лошади красивая грива, а копыта после дождя были мокрыми.

That would still be understandable.

Adding её makes the connection a little clearer and slightly more explicit. English uses possessives more often than Russian, so learners should know that Russian is often happy to leave them out when the meaning is obvious.

Because the preposition после (after) requires the genitive case.

So:

• дождь = rain, nominative
• после дождя = after the rain, genitive

This is just something you have to learn with the preposition:

• после урока = after the lesson
• после работы = after work
• после дождя = after the rain

Because the subject in that clause is копыта (hooves), which is plural.

The singular noun is:

• копыто = hoof

Plural:

• копыта = hooves

Since the subject is plural, the past tense form of быть is plural too:

• был = masculine singular
• была = feminine singular
• было = neuter singular
• были = plural

So:

• её копыта ... были мокрыми = her hooves were wet

This is about the predicate adjective after были.

In Russian, after forms of быть, an adjective describing the subject can appear in the instrumental case, especially in past and future constructions:

• были мокрыми

Here мокрыми is instrumental plural, agreeing with копыта.

So the structure is:

• копыта = plural
• мокрыми = instrumental plural adjective

You may also hear были мокрые in real speech. That is possible too. Very roughly:

• были мокрыми can sound a bit more standard or emphasize the state
• были мокрые is also common and natural

For a learner, the key point is that мокрыми is not random: it is the instrumental plural form of мокрый.

Each adjective agrees with its noun in gender, number, and case.

Here are the three examples:

• белой лошади

  • noun: лошади
  • feminine singular, genitive
  • so adjective: белой

• красивая грива

  • noun: грива
  • feminine singular, nominative
  • so adjective: красивая

• мокрыми копытами would be the full instrumental phrase

  • in the sentence, we only see the adjective as a predicate: копыта были мокрыми
  • plural instrumental
  • so adjective: мокрыми

So the different endings are there because the adjectives are matching different nouns in different grammatical roles.

Russian has no articles, so there is no direct equivalent of a or the.

That means:

• белая лошадь can mean a white horse or the white horse
• красивая грива can mean a beautiful mane or the beautiful mane, depending on context

English has to choose an article, but Russian usually leaves that to context.

In this sentence, English would most naturally say the white horse and a beautiful mane or the white horse has a beautiful mane, but Russian itself does not mark that difference with separate words.