El pulsador está detrás del decorado.

Because this sentence is talking about location, and in Spanish location is normally expressed with estar, not ser.

• El pulsador está detrás del decorado = the button/switch is behind the set
• Estar is used for where something is
• Ser is used for identity, characteristics, origin, etc.

So:

• Es un pulsador = It is a push-button / switch
• Está detrás del decorado = It is behind the set

This is one of the most important uses of estar.

Pulsador usually means a push-button, button, or sometimes a switch/control button, depending on context.

It comes from the verb pulsar, which means to press.

So a learner might think of it as:

• a button you press
• a push switch
• a control button

In everyday English, the best translation depends on the situation. In some contexts button sounds most natural; in others switch may fit better.

Here decorado means something like the set, stage set, or scenery.

It does not usually mean decoration in the general English sense. That is a common trap because it looks similar to the English word decorated/decoration.

So in this sentence, el decorado is probably:

• a theatrical set
• a TV or film set
• artificial scenery

Because de + el normally contracts to del in Spanish.

So:

• de + el = del

That is why you get:

• detrás del decorado

not

• detrás de el decorado

This contraction is required in standard Spanish.

A useful comparison:

• al = a + el
• del = de + el

Because detrás normally works with de when it is followed by a noun or pronoun.

So the pattern is:

• detrás de + noun/pronoun

Examples:

• detrás de la puerta = behind the door
• detrás del decorado = behind the set
• detrás de mí = behind me

You usually cannot say detrás el decorado. The de is part of the structure.

The accents show stress and also help distinguish forms.

• está has an accent because the stress falls on the last syllable: es-TÁ
• detrás has an accent because the stress falls on the last syllable: de-TRÁS

In está, the accent also helps distinguish it from esta, which can mean this:

• esta puerta = this door
• está detrás = is behind

So the accent matters both for pronunciation and meaning.

Because both nouns are masculine singular:

• el pulsador
• el decorado

Spanish uses articles more regularly than English does. In this sentence, both nouns are specific:

• the button/switch
• the set

That is why the definite article el appears with both.

Also, the article tells you the gender and number of the noun:

• el = masculine singular
• la = feminine singular
• los = masculine plural
• las = feminine plural

Yes, tras el decorado is possible and means essentially the same thing: behind the set.

However, there is a difference in feel:

• detrás de is very common and neutral
• tras is a bit more concise and can sound slightly more formal or literary in some contexts

So:

• El pulsador está detrás del decorado = very standard
• El pulsador está tras el decorado = also correct

For most learners, detrás de is the safest everyday choice.

Yes, but only when the thing it refers to is already clear from context.

For example:

• ¿Dónde está el pulsador?
• Está detrás.

Here detrás means behind / in the back, and you do not need to repeat the noun.

But if you want to say behind the set, then you need de:

• Está detrás del decorado

So:

• detrás alone = possible when the reference is understood
• detrás de + noun = needed when you name what something is behind

Yes, but El pulsador está detrás del decorado is the most natural neutral order.

This is the standard pattern:

• subject + verb + location

Other orders are possible, but they change the emphasis:

• Detrás del decorado está el pulsador = puts more emphasis on the location
• Está detrás del decorado el pulsador = possible in some contexts, but less neutral and less common as a simple standalone sentence

For learners, the original order is the best one to use.

In standard Spain Spanish, a rough pronunciation guide would be:

el pool-sah-THOR es-TA de-TRAS del deh-koh-RAH-doh

A few important points:

• z in pulsador is not present, but the c and z issue often matters in Spain Spanish; here it does not apply
• detrás ends with an s sound
• the stress is on:
  • pulsaDOR
  • esTÁ
  • deTRÁS
  • decoRAdo

A more careful IPA-style pronunciation would be approximately:

[el pulsaˈðoɾ esˈta deˈtɾaz del dekoˈɾaðo]

In many parts of Spain, the d between vowels can sound softer, especially in natural speech.

Yes, that is a useful pattern. Nouns ending in -or are very often masculine.

So:

• el pulsador
• el motor
• el color

This is not just because of the ending alone in every single case, but it is a strong and helpful pattern for learners.

Here, because pulsador is masculine singular, the article is el.

Yes. Se encuentra detrás del decorado is grammatically correct and means something like it is located behind the set.

But the tone is different:

• está detrás del decorado = simple, natural, everyday
• se encuentra detrás del decorado = more formal, descriptive, or written

In normal conversation, está is usually the better choice.