La rotura está junto a la ventana.

Because this sentence is talking about location.

In Spanish, estar is normally used for where something is:

• La rotura está junto a la ventana. = The break/damage is next to the window.

By contrast, ser is used more for identity, definition, or essential characteristics:

• Es una rotura pequeña. = It is a small break/damage.
• Es un problema grave. = It is a serious problem.

So here, since the sentence tells us where the damage is, estar is the correct verb.

Rotura usually means break, breakage, damage, or crack, depending on context.

It often refers to:

• something broken
• the place where something has broken
• the damage caused by a break

So in this sentence, la rotura could mean:

• the break
• the damaged area
• the crack/breakage

It is a noun, not an adjective. Compare:

• La rotura = the break / the damage
• Está roto = it is broken

Yes. Rotura is a feminine noun, so it takes the feminine singular article la.

That is why you get:

• la rotura
• not el rotura

This also affects any adjectives that agree with it:

• La rotura es pequeña.
• La rotura es visible.

A common clue is that many nouns ending in -a are feminine, though not all.

Spanish uses articles like el, la, los, and las more often than English does.

So where English might say:

• next to the window

Spanish naturally says:

• junto a la ventana

Even when English might leave the article out in some contexts, Spanish often keeps it. Here, la ventana is completely normal and expected.

Junto a means next to, beside, or right by.

It suggests close physical proximity.

So:

• La rotura está junto a la ventana. = The break/damage is next to the window.

Similar expressions are:

• al lado de = next to / beside
• cerca de = near

Nuance:

• junto a and al lado de usually suggest something quite close
• cerca de can be a bit less exact and can mean simply near

Because junto is normally followed by the preposition a when it means next to.

So the full structure is:

• junto a + noun

Examples:

• junto a la puerta = next to the door
• junto al coche = next to the car
• junto a la ventana = next to the window

This a is just part of the expression. You should learn junto a as a set phrase.

Because in Spanish, contraction only happens with:

• a + el = al
• de + el = del

But a + la does not contract.

So:

• junto a la ventana = correct
• junto al coche = correct, because a + el = al

Examples:

• Voy a la casa.
• Voy al parque.

Yes, absolutely.

These are both natural:

• La rotura está junto a la ventana.
• La rotura está al lado de la ventana.

They mean almost the same thing: the break/damage is next to the window.

A slight difference:

• junto a can sound a little more concise or formal in some contexts
• al lado de is very common in everyday speech

Both are good Spanish.

Yes, but the meaning changes slightly.

• La rotura está junto a la ventana.
  = The break/damage is next to the window.
  This refers to a specific break/damage.

• Hay una rotura junto a la ventana.
  = There is a break/damage next to the window.
  This introduces the existence of one.

So:

• está = says where something is
• hay = says that something exists / there is something

This is a very common Spanish distinction.

The given word order is the most neutral and natural:

• La rotura está junto a la ventana.

But Spanish can change word order for emphasis or style:

• Junto a la ventana está la rotura.

That sounds more marked or literary, and it puts extra focus on the location.

For everyday use, the original order is usually the best choice.

Not always. They are related, but they are not identical.

• rotura usually refers to a break, breakage, or physical damage
• ruptura often means rupture, separation, breaking off, or even a breakup in more abstract contexts

Examples:

• la rotura de una tubería = the break in a pipe
• la ruptura de relaciones = the breakdown of relations
• la ruptura de una pareja = a couple’s breakup

So in this sentence, rotura is the more natural word if we are talking about physical damage near a window.