Je vais au centre-ville en tram quand il pleut.

In French, the present tense often covers both:

• a habitual action: I go
• a current action: I am going

In this sentence, quand il pleut makes it sound habitual/general:

• Je vais au centre-ville en tram quand il pleut.
• I go to downtown / the city centre by tram when it rains.

So here je vais is best understood as I go or I take the tram downtown when it rains.

Because à + le contracts to au in French.

So:

• à + le = au
• à + les = aux

That gives:

• au centre-ville = to the city centre / downtown

You cannot normally keep à le as two separate words in standard French.

Centre-ville means city centre or downtown, depending on the variety of English you use.

It is a fixed noun expression:

• le centre-ville = the city centre / downtown

The hyphen is standard in this word. It is very common in French.

French usually uses en with many means of transport to mean by:

• en voiture = by car
• en bus = by bus
• en train = by train
• en tram = by tram

So en tram is the normal way to say by tram.

Avec le tram would sound more like with the tram and is not the normal way to express transportation here.

Yes. Both are possible.

• tramway is the full word
• tram is the common shorter everyday form

So these both work:

• en tram
• en tramway

In everyday speech, en tram is very natural.

When French uses en to express means of transport, it usually does not use an article.

So you say:

• en bus
• en train
• en avion
• en tram

Not:

• en le tram
• en un tram

This is just the normal French pattern for transportation.

In il pleut, the il does not refer to a person or thing. It is an impersonal subject.

French usually requires a subject before the verb, so weather expressions often use il:

• il pleut = it is raining / it rains
• il neige = it is snowing / it snows
• il fait froid = it is cold

This is similar to English it rains, where it also does not refer to anything specific.

Here it most naturally means whenever it rains or when it rains in a general sense.

Because the whole sentence is in the present tense and sounds habitual, the meaning is:

• Whenever it rains, I go downtown by tram.

French often uses quand this way for repeated situations.

Yes, absolutely.

You can say:

• Je vais au centre-ville en tram quand il pleut.
• Quand il pleut, je vais au centre-ville en tram.

Both are correct.

The second version puts more emphasis on the condition when it rains.

Putting it at the end is a very natural word order in French. The sentence first gives the main action, then adds the time/condition:

• Je vais au centre-ville en tram = main idea
• quand il pleut = when it rains

This structure is common and natural. It does not change the basic meaning.

Because aller à is the usual pattern for going to a place:

• aller au centre-ville = to go downtown / go to the city centre

By contrast:

• dans le centre-ville means in the city centre

So:

• Je vais au centre-ville = I go to downtown
• Je suis dans le centre-ville = I am in downtown

The first is about movement toward a place. The second is about location inside a place.

It most naturally describes a habit or usual behavior.

That is because:

• the verb is in the present tense
• quand il pleut gives a repeated situation

So the idea is:

• When it rains, I go downtown by tram.

If you wanted to make it clearly about right now, French would usually need more context, for example:

• Aujourd’hui, je vais au centre-ville en tram parce qu’il pleut.
• Today I’m going downtown by tram because it’s raining.

Yes. Vais is the first-person singular present form of aller:

• je vais = I go / I am going
• tu vas = you go
• il/elle va = he/she goes
• nous allons = we go
• vous allez = you go
• ils/elles vont = they go

So in this sentence, je vais comes from aller, meaning to go.

A native speaker would most likely understand it as a general habit:

• I go downtown by tram when it rains.
• or more naturally in English:
• When it rains, I take the tram downtown.

That is probably the most natural English-style interpretation of the French sentence.