El localizador aparece en el comprobante de facturación.

Because the subject is singular: el localizador.

• el localizador = one thing
• so the verb is aparece = it appears

If the subject were plural, you would use aparecen:

• Los localizadores aparecen en el comprobante de facturación.

The infinitive is aparecer, which means to appear or to show up.

In this sentence:

• aparece = appears
• It is 3rd person singular, present indicative

A quick pattern:

• yo aparezco
• tú apareces
• él/ella aparece
• nosotros aparecemos
• vosotros aparecéis
• ellos aparecen

Spanish usually uses the definite article more often than English does.

Here, el localizador refers to a specific item: the locator / booking reference that belongs to that receipt or booking.

So Spanish naturally says:

• El localizador aparece...

where English might sometimes say simply Locator appears... in very short labels or instructions, but in a full sentence Spanish normally keeps the article.

Not usually in a literal, general English sense.

In travel Spanish, especially in Spain, localizador often means a booking reference, record locator, or reservation code.

So even though the word looks like locator, in real-life travel contexts it usually refers to the code used to find a booking.

It is a noun phrase made up of:

• comprobante = proof, receipt, voucher, confirmation slip
• de facturación = of check-in / of billing / of invoicing, depending on context

So grammatically, de facturación modifies comprobante.

This noun + de + noun structure is very common in Spanish:

• billete de tren = train ticket
• tarjeta de crédito = credit card
• comprobante de facturación = check-in receipt / billing receipt / proof of check-in

Because Spanish very often links nouns with de where English might prefer a compound noun or adjective.

For example:

• centro de salud = health centre
• tarjeta de embarque = boarding pass
• comprobante de facturación = check-in receipt / billing receipt

Using de is one of the most natural ways in Spanish to say that one noun describes or specifies another.

No. This is a very important context word.

In general Spanish, facturación can mean billing or invoicing.
But in travel and airport contexts, especially in Spain, facturación often refers to check-in or baggage check-in.

So the exact meaning depends on the situation.

For example:

• mostrador de facturación = check-in desk
• comprobante de facturación = check-in receipt / proof of check-in

This is one reason why direct word-for-word translation can be misleading.

En is the normal preposition here because Spanish uses it for information that appears in/on a document, screen, list, form, or receipt.

So:

• aparece en el comprobante
• literally, appears in/on the receipt

English chooses between in and on depending on style, but Spanish very often just uses en.

You also see this with:

• en la pantalla = on the screen
• en la lista = on the list
• en el documento = in/on the document

Yes, you could, but the nuance is slightly different.

• aparece = appears / is shown
• está = is located / is there

So:

• El localizador aparece en el comprobante de facturación sounds like the locator is shown/printed on the receipt
• El localizador está en el comprobante de facturación sounds more like the locator is on the receipt

Both are understandable, but aparece is often better when talking about information displayed on a document or screen.

Yes. Spanish word order is flexible.

You could also say:

• En el comprobante de facturación aparece el localizador.

This version puts more emphasis on where it appears.

The original order is more neutral:

• El localizador aparece en el comprobante de facturación.

Both are correct.

Because comprobante is masculine in this meaning.

Its ending -e does not automatically make it feminine. In Spanish, grammatical gender is not always predictable just from the ending.

So you say:

• el comprobante
• un comprobante

This is something learners often need to memorize word by word.

Because the stress falls on the last syllable: -ción.

Without the written accent, Spanish stress rules would make you pronounce it differently. The accent tells you the correct stress:

• fac-tu-ra-ción

This is very common with nouns ending in -ción:

• información
• reservación
• confirmación
• facturación

Yes. It is in the present indicative.

Spanish often uses the present tense to state general facts, standard procedures, or what is normally the case.

So here it means something like:

• this is where the locator appears
• as a general rule, the locator is shown there

This is very common in notices, websites, instructions, and customer-service language.