L'entrevistador pregunta per l'experiència laboral.

Because el becomes l' before a singular noun that starts with a vowel or mute h.

• el entrevistador → l'entrevistador
• el home → l'home

This is just like an elision to make pronunciation smoother. The full article is still masculine singular el, but in writing it changes to l' before the vowel.

Entrevistador means interviewer.

It comes from the verb entrevistar (to interview) plus the ending -dor, which often means the person who does the action.

For example:

• entrevistar = to interview
• entrevistador = interviewer
• entrevistadora = female interviewer

So l'entrevistador means the interviewer.

In Catalan, preguntar per often means to ask about or to ask for information about something.

So:

• pregunta per l'experiència laboral = asks about work experience

This is different from:

• preguntar una cosa = to ask something
• preguntar a algú = to ask someone

Examples:

• Pregunta per tu. = He/She is asking about you.
• Pregunta l'hora. = He/She asks the time.
• Pregunta al professor. = He/She asks the teacher.

So here, per is important because it introduces the topic being asked about.

No. Although per often translates as for, it has several uses, and in this sentence it is better understood as about.

Here:

• preguntar per alguna cosa = to ask about something

So you should not translate word-for-word:

• pregunta per l'experiència laboral not literally asks for the work experience but rather asks about work experience

Catalan prepositions do not always match English ones directly.

Because the noun experiència is feminine singular, so its article is la. But la becomes l' before a vowel:

• la experiència → l'experiència

So:

• la taula = the table
• l'experiència = the experience

This is the same kind of elision as in l'entrevistador.

Laboral is an adjective meaning work-related or job-related.

So:

• experiència laboral = work experience

Catalan often uses an adjective where English may use a noun modifier:

• vida laboral = working life / employment record
• risc laboral = workplace risk / occupational risk

You could sometimes express similar ideas in other ways, but experiència laboral is the normal, natural phrase.

Pregunta is the third person singular present indicative of preguntar.

So it means:

• he asks
• she asks
• it asks
• or, in this context, the interviewer asks

Conjugation of preguntar in the present:

• jo pregunto = I ask
• tu preguntes = you ask
• ell/ella pregunta = he/she asks
• nosaltres preguntem = we ask
• vosaltres pregunteu = you all ask
• ells/elles pregunten = they ask

A simple approximate pronunciation is:

lun-treh-bees-tuh-DOR preh-GOON-tuh per lek-speh-ree-EN-see-uh luh-buh-RAL

A few helpful notes:

• ll / l' here is just a normal l
• v in many Catalan varieties sounds close to b
• x in experiència sounds like ks
• the stress is on:
  • entrevistaDOR
  • preGUNta
  • experiÈNcia
  • laboRAL

Pronunciation varies somewhat by dialect, but this will help you get close.

In this sentence, the article is natural and expected.

• L'entrevistador pregunta per l'experiència laboral. = The interviewer asks about the work experience.

If you remove it:

• pregunta per experiència laboral

that sounds less natural in a normal full sentence. Catalan usually uses the definite article more often than English does in cases like this.

Yes, sobre can also mean about, and in some contexts it works. But with preguntar, preguntar per is very common and idiomatic.

So:

• pregunta per l'experiència laboral = very natural
• pregunta sobre l'experiència laboral = understandable, but often less idiomatic in this kind of sentence

For learners, it is best to remember:

• preguntar per + topic/person = ask about

It is neutral and standard. It would fit very naturally in:

• a textbook
• a job interview context
• a description of what happens during an interview

Nothing in the sentence is especially formal or informal. It is just normal correct Catalan.

You would change entrevistador to entrevistadora:

• L'entrevistadora pregunta per l'experiència laboral.

The article still becomes l' because entrevistadora begins with a vowel.

So:

• l'entrevistador = the male interviewer
• l'entrevistadora = the female interviewer