Mira el mapa abans d'anar a l'aeroport.

Mira is the informal singular imperative of mirar (to look at / to check).

So the sentence is addressing one person informally, like you in English.

• mirar → mira! = look!
• Formal singular: miri
• Informal plural: mireu
• Formal plural: mirin

A small detail: mira is also the same form as the present tense for he/she/you-formal (ell/ella/vostè mira), but in this sentence the meaning is clearly a command.

Catalan often drops subject pronouns when they are understood from the verb form.

So Mira el mapa... already means You look at the map... / Look at the map...

Adding tu is possible, but usually only for emphasis or contrast:

• Tu mira el mapa... = You look at the map... (with extra emphasis)

Most of the time, Catalan sounds more natural without the pronoun.

Because mapa is being used as a specific noun, so Catalan uses the definite article el.

• el mapa = the map
• un mapa = a map

In commands like this, Catalan normally keeps the article:

• Mira el mapa = Look at the map
• Compra un mapa = Buy a map

English sometimes drops articles in short instructions, but Catalan usually does not.

Because Catalan uses abans de + infinitive to mean before doing something.

So:

• abans de
  • anar = before going

Since anar begins with a vowel, de becomes d':

• de anar → d'anar

This apostrophe is a normal spelling change in Catalan.

Use abans de + infinitive when the subject is understood and usually the same as the main subject.

• Mira el mapa abans d'anar a l'aeroport. = Look at the map before going to the airport. = the person who looks is also the person who goes

Use abans que + verb when you need a full clause, especially if the subject is different.

• Mira el mapa abans que ell vagi a l'aeroport. = Look at the map before he goes to the airport.

This is a very common pattern in Catalan.

Because anar (to go) normally takes the preposition a before a destination:

• anar a casa
• anar a l'escola
• anar a l'aeroport

Then Catalan also uses the definite article with aeroport:

• el aeroport would not be correct in modern spelling
• el + aeroport becomes l'aeroport

So:

• a + l'aeroport = to the airport

Because the definite article el becomes l' before a vowel or silent h.

• el mapa
• l'aeroport
• l'hotel

So:

• el aeroport → l'aeroport

This is called apostrophe/elision, and it is required in normal spelling.

They show that a vowel has been dropped to make pronunciation smoother.

Two things happen here:

• de + anar → d'anar
• el + aeroport → l'aeroport

Catalan does this very often before words beginning with a vowel.

So the apostrophes are not optional punctuation; they are part of the correct written form.

Because mirar means to look at, to watch, or to check, while veure means to see.

In this sentence, the idea is intentional: check the map / look at the map. That fits mirar.

Compare:

• Mira el mapa = Look at / Check the map
• Veig el mapa = I see the map

So mirar is the natural choice for giving this instruction.

Historically, yes, since de is the same word that often means of, but in this structure you should learn it as a fixed pattern:

• abans de + infinitive = before doing something

So it is better not to translate word by word. Instead, treat:

• abans d'anar a l'aeroport as before going to the airport

That will help you sound more natural.

As written, it is informal singular: you are speaking to one person using tu.

• Mira el mapa... = informal singular

Other versions would be:

• Miri el mapa abans d'anar a l'aeroport. = formal singular
• Mireu el mapa abans d'anar a l'aeroport. = informal plural
• Mirin el mapa abans d'anar a l'aeroport. = formal plural

So the original sentence is specifically talking to one person informally.