La professora li explica la resposta a la meva filla.

Li is an indirect object pronoun. Here it means to her, referring to a la meva filla.

So the structure is:

• La professora = the teacher
• li explica = explains to her
• la resposta = the answer
• a la meva filla = to my daughter

A useful thing to know is that li does not show gender by itself. It can mean:

• to him
• to her
• to you (formal singular)

In this sentence, we know it means to her because of a la meva filla.

This is because Catalan very often uses clitic doubling, especially with indirect objects.

So Catalan commonly says both:

• the pronoun: li
• the full noun phrase: a la meva filla

That may feel redundant to an English speaker, because English usually says only to my daughter, not to her to my daughter. But in Catalan, this doubling is normal and very natural.

So:

• La professora li explica la resposta a la meva filla.

is a very natural Catalan sentence.

Because a introduces the indirect object, the person who receives something.

Here, the thing being explained is:

• la resposta = the answer

And the person receiving the explanation is:

• a la meva filla = to my daughter

So a works like English to here.

Compare:

• explicar una cosa a algú = to explain something to someone

That is the normal pattern.

In this sentence:

• la resposta is the direct object
• li / a la meva filla is the indirect object

Why?

• The teacher explains what? → la resposta
• The teacher explains the answer to whom? → a la meva filla

So the sentence structure is:

• Subject: La professora
• Indirect object pronoun: li
• Verb: explica
• Direct object: la resposta
• Full indirect object phrase: a la meva filla

In standard Catalan, possessives are usually used with an article.

So Catalan normally says:

• la meva filla = my daughter
• el meu pare = my father
• la nostra casa = our house

This is different from English, where you just say my daughter without the.

So although English has no article here, Catalan normally does.

There are a few special or more literary/regional cases where the article may be omitted, but for a learner, la meva filla is the standard and safest form.

Catalan uses definite articles in many places where English also uses the.

Here:

• la professora = the teacher
• la resposta = the answer

These are specific, identifiable things in the sentence.

If you wanted a teacher or an answer, you would use the indefinite article instead:

• una professora = a teacher
• una resposta = an answer

So the use of la here is just the normal definite article, feminine singular.

Explica is the:

• present indicative
• third person singular
• from the verb explicar = to explain

So it matches la professora:

• La professora explica = The teacher explains / is explaining

A quick mini-pattern:

• jo explico = I explain
• tu expliques = you explain
• ell/ella explica = he/she explains

You may sometimes hear or see:

• La professora explica la resposta a la meva filla.

and it can be understood perfectly well.

However, with an indirect object, Catalan very often prefers to include the clitic pronoun too:

• La professora li explica la resposta a la meva filla.

That version is usually more natural in everyday Catalan. So for learners, it is a good idea to get used to this pattern.

Yes, Catalan word order is somewhat flexible, although some versions are more neutral than others.

The sentence you have is a normal order:

• La professora li explica la resposta a la meva filla.

You could also move the indirect object phrase for emphasis:

• A la meva filla, la professora li explica la resposta.

This puts extra focus on my daughter.

What usually stays the same is that the clitic pronoun li goes before the conjugated verb:

• li explica

That is an important pattern in Catalan.

Yes. If the teacher were explaining the answer to more than one person, the indirect object pronoun would usually be els.

For example:

• La professora els explica la resposta als meus fills.
• The teacher explains the answer to my children.

So:

• li = to him / to her / to you (formal singular)
• els = to them / to you (formal plural)

That is a very useful contrast to learn early.