¿De qué trata la película?

Because the expression is tratar de when it means to be about.

So Spanish asks literally something like About what does the film deal?

• de = about / of
• qué = what

When a verb needs a preposition, Spanish keeps that preposition before qué in the question:

• La película trata de amor.
• ¿De qué trata la película?

Here trata comes from the verb tratar.

In this sentence, tratar de means:

• to be about
• to deal with

So ¿De qué trata la película? uses trata in the sense of is about, not tries or treats.

Be careful, because tratar de + infinitive can also mean to try to:

• Trato de estudiar. = I try to study.

But with a subject like la película, the meaning is clearly to be about.

Because the subject is singular: la película.

• la película = singular
• so the verb must also be singular: trata

If the subject were plural, you would say:

• ¿De qué tratan las películas?

That word order is very normal in Spanish questions.

Spanish often puts:

• question word
• verb
• subject

So ¿De qué trata la película? sounds natural and standard.

You may also hear similar patterns like:

• ¿Dónde está el libro?
• ¿Qué dice el profesor?

Putting the subject after the verb is especially common in questions.

Not normally. It sounds unnatural in standard Spanish.

The natural form is:

• ¿De qué trata la película?

Spanish usually moves the question word phrase to the front. So de qué goes first.

A version like ¿La película de qué trata? is possible in very marked or contrastive speech, but it is not the basic form learners should use first.

Yes, very close.

In Spain, ¿De qué va la película? is very common and natural in everyday speech. It also means What is the film about?

Difference in tone:

• ¿De qué trata la película? = neutral, standard
• ¿De qué va la película? = very common, a bit more conversational

Both are good, especially in Spain.

No. You need de here.

That is because with this meaning, the structure is tratar de + topic:

• La película trata de la guerra.
• El libro trata de amistad.

So the question must also keep de:

• ¿De qué trata la película?

Yes.

qué takes an accent when it is used in a question or exclamation, whether direct or indirect.

So:

• ¿Qué es eso?
• No sé qué quiere.
• ¿De qué trata la película?

Without the accent, que is usually a different word, often meaning that or which.

Because the stress falls on lí: pe-LÍ-cu-la.

Spanish spelling rules require a written accent on words stressed on the third-from-last syllable. Words like that are called esdrújulas, and they always have a written accent.

So:

• película
• música
• teléfono

A simple guide is:

de KE tra-ta la pe-LI-ku-la

More naturally in Spain:

• de = short and light
• qué = stressed
• trata = stress on tra
• película = stress on lí

So the main stressed parts are:

• qué
• tra
• lí

Yes, if you mean the film.

• la película = the film / the movie
• una película = a film / a movie

If the film is already understood from context, you can drop the noun entirely:

• ¿De qué trata? = What is it about?

But if you say the full sentence, la is correct and necessary before película.

Not in every meaning, but in this meaning, yes.

Useful distinction:

• tratar de + noun/topic = to be about
• tratar de + infinitive = to try to
• tratar algo = to deal with / discuss something

Examples:

• La película trata de un robo. = The film is about a robbery.
• Trato de dormir. = I try to sleep.
• El libro trata un tema difícil. = The book deals with a difficult topic.

For your sentence, the pattern to remember is:

• ¿De qué trata...?

A very common answer pattern is:

• Trata de... = It’s about...

Examples:

• Trata de una familia que se muda a Madrid.
• Trata de un detective.
• Trata de la guerra civil.

In Spain, with ir de, you may also hear:

• Va de...

For example:

• Va de un chico que viaja en el tiempo.