Die Blätter rascheln im Wind vor dem Fenster.

Die is also the definite article for plural nouns in the nominative case.

So here:

• singular: das Blatt = the leaf
• plural: die Blätter = the leaves

In this sentence, die Blätter is the subject, so die is the normal nominative plural article.

The singular is das Blatt.

Its plural is die Blätter. German often forms plurals by adding an ending and sometimes also changing the vowel with an umlaut:

• a → ä
• Blatt → Blätter

So the plural changes in two ways:

• -er is added
• a becomes ä

This is very common in German noun plurals, but it has to be learned word by word.

Because the subject is plural: die Blätter.

The verb rascheln is conjugated like this:

• ich raschle
• du raschelst
• er/sie/es raschelt
• wir rascheln
• ihr raschelt
• sie rascheln

With die Blätter = they, you need sie rascheln.
That is why the sentence uses rascheln.

A common thing that confuses learners is that the 3rd person plural form is identical to the infinitive.

Not exactly.

Rascheln describes a light, dry, rustling sound, especially from things like:

• leaves
• paper
• dry grass
• clothing

So it fits Blätter very naturally.

Rauschen usually suggests a broader, more continuous rushing or whooshing sound, such as:

• wind in trees
• water
• traffic in the distance

So rascheln is more specific and more delicate here.

Im is just the contraction of in dem:

• in dem → im

This contraction is extremely common and usually preferred when it sounds natural.

So:

• im Wind = in dem Wind

It means the leaves are rustling in the wind.

Because in is a two-way preposition. It can take either:

• accusative for direction/movement toward somewhere
• dative for location

Here there is no movement into the wind. The phrase describes the situation or setting in which the rustling happens. So German uses dative:

• im Wind = in dem Wind

Compare:

• Die Blätter rascheln im Wind. = location/situation
• Die Blätter fallen in den Garten. = movement into the garden

For the same reason: vor is also a two-way preposition.

It takes:

• dative for location
• accusative for movement toward a position

In this sentence, vor dem Fenster describes where the leaves are: in front of the window / outside the window area. That is a location, so German uses dative:

• vor dem Fenster

If something moved to that position, you would use accusative:

• Er stellt den Stuhl vor das Fenster.
  He places the chair in front of the window.

Dem Fenster is dative singular.

The noun Fenster is neuter:

• nominative: das Fenster
• dative: dem Fenster

Many German nouns do not change their form in the dative singular. The article changes, but the noun stays the same.

So the important case marker here is mainly the article:

• das Fenster
• dem Fenster

It can suggest either, depending on context.

Literally, vor dem Fenster means in front of the window. But in real usage, with something like leaves and wind, it will often be understood as something like:

• outside the window
• in front of the window
• just beyond the window

So the phrase is spatial, and the exact English wording depends on context.

Yes. German word order is flexible, but in a main clause the finite verb must stay in second position.

The basic version is:

• Die Blätter rascheln im Wind vor dem Fenster.

You could also say:

• Im Wind rascheln die Blätter vor dem Fenster.
• Vor dem Fenster rascheln die Blätter im Wind.

These versions shift emphasis, but they are still grammatical because rascheln remains the second element.

Grammatically, it functions as an adverbial phrase of place, so it tells you where the situation happens.

In practice, that means it relates to the whole scene: the leaves are there, and the rustling happens there. You do not usually need to separate those two ideas sharply.

So a learner can safely understand it as: this is the location of the leaves/rustling.

Sometimes, but it changes the meaning.

• vor dem Fenster = in front of the window / outside the window area
• am Fenster = at the window / by the window

With Blätter, vor dem Fenster sounds more natural if you mean leaves outside.
Am Fenster could sound as if the leaves are right by the window or somehow attached to its immediate area.

So vor dem Fenster is the better choice for the image in this sentence.

Because in German, all nouns are capitalized, not just proper names.

So in this sentence:

• Blätter
• Wind
• Fenster

are all capitalized because they are nouns.

This is one of the most visible spelling rules in German.

German present tense can do both, just like English present forms can depend on context.

So Die Blätter rascheln im Wind vor dem Fenster could mean:

• they are rustling now
• they rustle there in that situation
• a vivid present description in a story

Without more context, the sentence is simply a present-time description.