Acerca la silla a la mesa para cenar juntos.

Here acerca is the tú affirmative imperative of acercar, meaning bring/move closer.

So:

• acercar = to bring/move something closer
• acerca = bring/move ... closer (informal command to one person)

That is different from:

• acerca de = about / concerning

So in this sentence, Acerca la silla... is a verb, not the expression acerca de.

It is the informal singular command used with tú.

So the sentence is speaking to one person in an informal way:

• (Tú) acerca la silla... = Bring the chair closer...

Other versions would be:

• Acerque la silla... = formal singular (usted)
• Acercad la silla... = informal plural in Spain (vosotros)
• Acerquen la silla... = formal plural, or plural in Latin America (ustedes)

That a is the preposition to / toward.

With acercar, Spanish often uses this pattern:

• acercar algo a algo = bring something closer to something

So:

• la silla = the chair
• a la mesa = to the table

This is not the personal a. It is just the normal preposition showing the destination or point of reference.

Spanish uses definite articles much more often than English.

Here:

• la silla = the chair
• la mesa = the table

Both nouns are feminine singular, so they take la.

In natural Spanish, using the article here sounds normal because the chair and table are understood from the situation. English often drops the in some contexts where Spanish keeps it less freely.

Acercar can be non-reflexive or reflexive, depending on what is moving.

In this sentence:

• Acerca la silla a la mesa = Move the chair closer to the table
• The object being moved is the chair, so the non-reflexive verb acercar is used.

If you were telling a person to move themselves closer, you would use the reflexive form:

• Acércate a la mesa = Come closer to the table

So:

• acercar algo = move something closer
• acercarse = move oneself closer

Para + infinitive is the normal way to express purpose when no new finite subject is introduced.

So:

• para cenar juntos = to eat dinner together / in order to have dinner together

Spanish also allows:

• para que + subjunctive

For example:

• Acerca la silla a la mesa para que podamos cenar juntos.

That version is a bit more explicit: so that we can have dinner together.

In your sentence, para cenar juntos is shorter and very natural.

Juntos means together, and it refers to the people who are going to have dinner together.

Usually that would mean something like:

• you and I
• or all of us present

Spanish does not need to spell that out if the context is obvious.

So para cenar juntos means:

• so we can eat dinner together
• literally, to dine together

Because Spanish adjectives must agree in gender and number with the people they refer to.

• juntos = masculine plural
• juntas = feminine plural

Spanish uses the masculine plural when:

• the group is all male, or
• the group is mixed, or
• the gender is unspecified

So juntos is the default form unless the speaker is referring to an all-female group.

Spanish often omits subject pronouns because the verb form already gives enough information.

So:

• Acerca la silla... already implies tú
• ...para cenar juntos can imply nosotros or we, depending on context

You could add pronouns for emphasis:

• Tú acerca la silla...
• ...para que nosotros cenemos juntos

But that would usually sound unnecessary in normal speech.

It follows a very common pattern:

Verb + direct object + destination/complement + purpose

So:

• Acerca = verb/command
• la silla = direct object
• a la mesa = where to move it / closer to what
• para cenar juntos = purpose

A very literal breakdown is:

• Bring the chair closer to the table in order to dine together.

That is why the word order feels natural in Spanish.

Yes. If the chair is already understood, you can use a direct object pronoun:

• Acércala a la mesa. = Bring it closer to the table.

Notice two things:

1. la replaces la silla
2. the command gets a written accent: Acércala

The accent is added to keep the normal stress after attaching the pronoun.

This is very common with affirmative commands in Spanish.

Yes, it is natural and correct in Spain.

A speaker in Spain might also say things like:

• Acerca la silla a la mesa.
• Arrima la silla a la mesa.
• Pon la silla más cerca de la mesa.

The original sentence is neutral and standard.
Arrimar can sound more colloquial in some regions, while poner la silla más cerca is a very everyday alternative.

Yes.

• cenar = to have dinner / to eat the evening meal
• comer = to eat / to have a meal (often lunch in Spain, depending on context)

So para cenar juntos specifically points to dinner, not just eating in general.