У стойки регистрации я показал паспорт и посадочный талон.

Here у means by, at, near.

So у стойки регистрации means at the check-in counter / by the check-in desk.

A useful pattern is:

• у + genitive = at / by / near someone or something

Examples:

• у окна = by the window
• у двери = by the door
• у входа = by the entrance

So this phrase is not literally saying inside the counter area, but at that location.

Because the preposition у requires the genitive case.

The dictionary form is:

• стойка = counter, stand, desk

After у, it changes to genitive singular:

• стойка → стойки

So:

• у стойки = at the counter

This is a very common case pattern in Russian: the preposition determines the case.

Because регистрации depends on стойки and means of registration.

Literally, стойка регистрации is:

• стойка = counter
• регистрации = of registration

So the whole phrase is literally counter of registration, which English expresses as check-in counter or registration desk.

The dictionary form is:

• регистрация = registration, check-in

Here it becomes genitive singular:

• регистрация → регистрации

This kind of noun + noun structure is extremely common in Russian:

• центр города = city center
• чашка чая = cup of tea
• стойка регистрации = check-in counter

Russian often allows the subject pronoun to be omitted if it is clear from context.

So both are possible:

• Я показал паспорт и посадочный талон.
• Показал паспорт и посадочный талон.

Including я makes the subject more explicit. It can add a little emphasis or simply make the sentence clearer, especially in teaching examples or when contrasting with someone else.

So:

• я показал = I showed
• показал alone can also mean I showed, if the context already makes that clear

Показал is the past tense masculine singular form of the verb показать.

It tells us two things:

1. The action happened in the past
2. The speaker is grammatically masculine

Compare:

• я показал = I showed (male speaker)
• я показала = I showed (female speaker)
• мы показали = we showed

So if a woman is saying this sentence, she would normally say:

• У стойки регистрации я показала паспорт и посадочный талон.

This is about aspect, which is very important in Russian.

• показать / показал = perfective
• показывать / показывал = imperfective

Here показал is used because the action is presented as a completed single event:

• I showed the documents, and that action was done.

Показывал would sound more like:

• I was showing
• I used to show
• I showed repeatedly
• the action is described without focusing on completion

At an airport check-in desk, showing your documents is usually a one-time completed action, so показал is the natural choice.

They are direct objects, so they are in the accusative case.

However, for inanimate masculine nouns, the accusative often looks exactly like the nominative.

So:

• паспорт

  • nominative: паспорт
  • accusative: паспорт

• посадочный талон

  • nominative: посадочный талон
  • accusative: посадочный талон

That is why they appear unchanged.

If the object were animate masculine, you would often see a different form:

• я вижу брата = I see my brother

But with inanimate nouns like паспорт and талон, the accusative matches the basic form.

Russian often leaves out possessive words like мой when ownership is obvious from context.

In this situation, if someone says:

• я показал паспорт и посадочный талон

it is naturally understood as:

• I showed my passport and my boarding pass

Using мой is possible, but often unnecessary:

• я показал мой паспорт
• я показал свой паспорт

These sound more explicit. In many everyday situations, Russian prefers the simpler version without the possessive.

This is very common with personal items, body parts, documents, clothing, and so on, when the owner is obvious.

Yes, you could, but свой is usually better than мой when the thing belongs to the subject of the sentence.

So these are possible:

• Я показал свой паспорт и посадочный талон.
• Я показал мой паспорт и посадочный талон.

But свой is more natural, because it refers back to the subject я:

• свой = one’s own

Russian often prefers свой when the subject owns the object:

• Я взял свой телефон.
• Она открыла свою сумку.

Still, in this sentence, native speakers would very often omit the possessive altogether.

Посадочный талон means boarding pass.

The parts are:

• посадочный = boarding, related to boarding
• талон = slip, pass, voucher, ticket-like document

So literally it is something like boarding slip/pass.

This is the standard expression in Russian for an airport boarding pass.

Because it must agree with талон.

The noun талон is:

• masculine
• singular
• here accusative inanimate, which looks like nominative

So the adjective also takes the matching form:

• посадочный талон

Russian adjectives agree with the nouns they describe in:

• gender
• number
• case

That is why you get:

• посадочный талон
  not something like посадочная or посадочное

Yes, Russian word order is fairly flexible, though different orders can change emphasis.

The original sentence:

• У стойки регистрации я показал паспорт и посадочный талон.

This emphasizes the setting first: at the check-in counter.

Other possible orders:

• Я показал паспорт и посадочный талон у стойки регистрации.
  More neutral, closer to English word order.

• Паспорт и посадочный талон я показал у стойки регистрации.
  This gives more emphasis to the documents.

• Я у стойки регистрации показал паспорт и посадочный талон.
  Also possible, though slightly less neutral.

So the original version is natural and puts the location at the front.

Russian has no articles.

So nouns like:

• стойка
• паспорт
• талон

do not need words corresponding to a, an, or the.

Whether something is understood as a passport, the passport, or my passport depends on context.

In this sentence, context makes it clear that the speaker means specific travel documents.

This is one of the big differences between English and Russian: English uses articles constantly, but Russian does not use them at all.

A stress-marked version is:

• У сто́йки регистра́ции я показа́л па́спорт и поса́дочный тало́н.

Rough pronunciation help:

• у = oo
• сто́йки = STOY-kee
• регистра́ции = ree-gyee-STRA-tsii
• я = ya
• показа́л = pa-ka-ZAL
• па́спорт = PAS-part
• поса́дочный = pa-SA-da-chny
• тало́н = ta-LON

A learner should especially remember the stress in:

• регистра́ции
• показа́л
• тало́н