La correa está detrás de la puerta, al lado de la mochila.

Because estar is used for location.

• La correa está detrás de la puerta = the leash/strap is behind the door.
• Ser (es) is normally used for identity, definition, origin, and more permanent characteristics.

So in Spanish, when you say where something is, you usually use estar:

• El libro está en la mesa.
• La mochila está en el suelo.

Correa can mean several things depending on context, including:

• strap
• belt
• leash

In a sentence like this, it often means strap or leash. The exact meaning depends on the situation you already know from context.

Because detrás normally needs de before the noun that follows.

So you say:

• detrás de la puerta = behind the door
• detrás de la casa = behind the house

This is like a fixed expression: detrás de + noun/pronoun.

You can sometimes use detrás on its own if the reference is already clear:

• Está detrás. = It is behind / in the back.

The accent mark shows the correct stress: de-TRÁS.

Without getting too technical, the written accent is needed because otherwise standard Spanish spelling rules would suggest a different stress pattern. So the accent helps show the word is pronounced correctly.

Al lado de means next to or beside.

In the sentence:

• al lado de la mochila = next to the backpack

It is another fixed expression:

• al lado de la mesa = next to the table
• al lado del coche = next to the car

Because al is the contraction of a + el.

However, in al lado de, the al is part of the set expression al lado de, which means next to / beside.

Compare:

• al lado de la mochila
• al lado del armario

So learners should usually just memorize al lado de as one chunk.

Spanish uses definite articles (el, la, los, las) more often than English does.

Here, each noun is feminine singular, so it takes la:

• la correa
• la puerta
• la mochila

In English, you might sometimes drop the, but in Spanish it is often required.

You usually learn the gender together with the noun:

• la correa
• la puerta
• la mochila

Many nouns ending in -a are feminine, which helps here, but that is only a tendency, not a perfect rule. The safest habit is to memorize each noun with its article.

This is a very normal Spanish word order:

• La correa = subject
• está = verb
• detrás de la puerta = first location phrase
• al lado de la mochila = extra detail about location

So the sentence builds the location in layers:

1. It is behind the door.
2. More specifically, it is next to the backpack.

This structure sounds natural in Spanish.

The comma separates two location phrases and makes the sentence easier to read.

• detrás de la puerta
• al lado de la mochila

It suggests a slight pause. In many contexts, Spanish speakers might also say the sentence without the comma in casual writing, but with the comma it is very clear and natural.

In some varieties of Spanish, atrás de is used, but for standard Spain Spanish, detrás de is more natural and more widely taught.

So for Spanish from Spain, detrás de la puerta is the safer choice.

There is nothing especially Spain-specific in the spelling of this sentence, but pronunciation in Spain would typically be:

• correa: the rr is a strong rolled sound
• puerta: the r is a single tap
• detrás: stress on the last syllable

A rough pronunciation guide could be:

la ko-RRE-a es-TA de-TRAS de la PWER-ta, al LA-do de la mo-CHI-la

The biggest thing learners often notice is the strong rr in correa.

Yes. Depending on the context, Spanish speakers might also use:

• la correa = leash / strap
• la correa del perro = the dog’s leash
• sometimes la traílla or other regional words, but these are less universal

For a general beginner sentence, la correa is completely normal and useful.

Because both are fixed prepositional expressions:

• detrás de
• al lado de

English uses different structures like behind the door and next to the backpack, but Spanish commonly forms these location expressions with de before the noun.

It is best to learn them as full chunks rather than translating word by word.