Mi perro se acerca a la puerta cuando oye el timbre.

My dog comes closer to the door when he hears the doorbell.

Breakdown of Mi perro se acerca a la puerta cuando oye el timbre.

• mi: my
• el perro: the dog
• la puerta: the door

Questions & Answers about Mi perro se acerca a la puerta cuando oye el timbre.

Why does it say se acerca and not just acerca?

In Spanish, acercarse (with se) means “to move/get closer (to something)”. It’s used reflexively, because the subject is moving itself.

• Mi perro se acerca a la puerta.
  My dog moves/comes closer to the door.

Without se, acercar is usually transitive: you move something else closer.

• Acerca la silla a la mesa.
  Move the chair closer to the table.

So in your sentence, the dog is moving itself closer, so you need se acerca.

Why is it a la puerta instead of just la puerta?

With acercarse, Spanish uses the preposition a to mark the thing you approach:

• acercarse a algo / a alguien = to get close to something / someone

So you must say:

• Mi perro se acerca a la puerta. ✅
  not Mi perro se acerca la puerta. ❌

Think of it like “gets close to the door” — the a is the “to”.

What does the se in se acerca refer to? Is it “himself”?