Реквизиты карты никому не показывайте.

In this sentence, реквизиты means the card’s details or information needed to use/identify it.

With a bank card, this can include things like:

• the card number
• expiry date
• cardholder name
• sometimes security-related details

It is normally used as a plural noun in Russian, much like details in English. So реквизиты карты is very natural for card details.

Because карты is in the genitive singular.

The phrase реквизиты карты literally works like:

• реквизиты = details
• карты = of the card

So the structure is basically the details of the card.

This is a very common pattern in Russian:

• номер телефона = phone number
• обложка книги = cover of the book
• реквизиты карты = card details

Because the verb показывать often takes:

• a direct object = what is being shown
• an indirect object in the dative = to whom it is being shown

So here:

• реквизиты карты = what you are showing
• никому = to nobody / to no one

The logic is:

• показывать что? = to show what?
• показывать кому? = to show to whom?

So никому не показывайте literally means do not show [them] to anyone.

Russian usually prefers the imperfective imperative for general negative instructions:

• не показывайте = don’t show / never show

This sounds like a normal rule, warning, or standing instruction.

The verb показывать is imperfective. Its perfective partner is показать.

Very roughly:

• не показывайте = don’t show it, as a rule
• не покажите would sound unusual here

In warnings and instructions, Russian commonly uses:

• Не курите. = Don’t smoke.
• Не входите. = Do not enter.
• Не сообщайте пароль. = Do not give your password.
• Не показывайте реквизиты карты. = Do not show your card details.

Because this is the imperative form, and specifically the polite/plural imperative.

From показывать, you get:

• показывай = show! / don’t show! when speaking to one person informally
• показывайте = show! / don’t show! when speaking:
  • politely to one person, or
  • to more than one person

So this sentence is either:

• a polite warning to one person, or
• an instruction addressed to multiple people

In public notices, customer messages, and formal instructions, -йте forms are very common.

Yes, it sounds polite/formal rather than casual.

Using показывайте instead of показывай makes it appropriate for:

• bank messages
• security warnings
• customer service language
• notices for the general public

A bank, website, or employee would naturally say:

• Реквизиты карты никому не показывайте.

To a close friend, you might also hear:

• Никому не показывай реквизиты карты.

Same idea, but more informal.

Yes, the word order could be different. Russian word order is more flexible than English.

This sentence could also be:

• Никому не показывайте реквизиты карты.
• Не показывайте никому реквизиты карты.

All of these are grammatical.

The version you were given starts with Реквизиты карты, which puts the focus first on the card details themselves. That works well in warnings, where the important object is often mentioned first.

A version beginning with Никому puts stronger emphasis on to no one.

It means to nobody / to no one, but in natural English we often translate the whole phrase as don’t show it to anyone.

This is a very important Russian pattern:

• никто не = nobody doesn’t? No — in Russian this correctly means nobody
• ничего не = nothing
• никому не = to nobody / to no one

Russian normally uses negative pronouns together with the negative particle не.

So:

• никому не показывайте literally = show to no one not
• natural meaning = don’t show it to anyone

This double negative is standard in Russian.

Yes, sometimes, but the nuance is a little different.

• реквизиты карты sounds very common in banking, payments, and security language
• данные карты also means card data/details, and is common too

In many situations they are close in meaning. But реквизиты often sounds a bit more like official/payment details, while данные is broader and more general.

For a security warning, реквизиты карты sounds very natural.

Good question. Literally, показывать means to show. But in a sentence like this, it is often understood more broadly in a security context:

• don’t show the card
• don’t reveal the details
• don’t let others see them

If you want to explicitly include telling someone, Russian might use verbs like:

• сообщать = to communicate, tell
• передавать = to pass on
• разглашать = to disclose

For example:

• Никому не сообщайте реквизиты карты. = Do not tell anyone your card details.
• Не разглашайте реквизиты карты. = Do not disclose your card details.

But не показывайте is still very natural if the warning is about letting others see the information.

Because Russian often leaves out the subject pronoun when the verb already shows who is meant.

Here, показывайте already tells you this is an imperative addressed to:

• you politely, or
• you all

So Russian does not need вы.

If you added it, it would usually sound more emphatic:

• Вы никому не показывайте реквизиты карты.

But the normal neutral version is without the pronoun.

It is a completely natural standalone sentence.

It sounds like the kind of brief instruction you might see:

• in a banking app
• in a fraud warning
• in a text message from a bank
• in a customer security notice

Russian often uses short imperative sentences for warnings, so this sounds perfectly complete and idiomatic.