Dopo la lezione, torno a casa in tram.

Tornare means to return / to go back, while andare means to go.

So torno a casa specifically means I go back home / I return home.
If you said vado a casa, that would mean I’m going home, but it does not emphasize the idea of returning in the same way.

Because the sentence starts with Dopo la lezione (After the lesson), torno is very natural: it suggests going back home once the lesson is finished.

Torno is the 1st person singular, present tense of tornare:

• io torno = I return / I go back
• tu torni = you return
• lui/lei torna = he/she returns

In Italian, the present tense is often used where English might say either I return, I go back, or even I’m going back, depending on context.

Italian often leaves out subject pronouns when they are clear from the verb ending.

Here, torno already tells you the subject is I, because the -o ending marks io.

So:

• (io) torno a casa = I go back home

Including io is possible, but it usually adds emphasis or contrast:

• Io torno a casa, lui resta qui.
  I’m going home, he’s staying here.

In Italian, a casa is a fixed, very common expression meaning home in the sense of to/at home.

So:

• vado a casa = I go home
• sono a casa = I’m at home
• torno a casa = I return home

Using alla casa would usually mean to the house, referring to a specific building, not home in the usual personal sense.

Compare:

• Torno a casa. = I’m going back home.
• Vado alla casa di Marco. = I’m going to Marco’s house.

In tram means by tram.

In Italian, in is commonly used with many means of transport:

• in treno = by train
• in autobus = by bus
• in macchina = by car
• in tram = by tram

So torno a casa in tram means that the tram is the means of transport.

They are different.

• in tram = by tram, using the tram as transport
• sul tram = on the tram, focusing on being physically aboard it
• con il tram is much less natural for this meaning

So if you are simply saying how you travel home, in tram is the normal choice.

Examples:

• Vado al lavoro in tram. = I go to work by tram.
• Sono sul tram adesso. = I’m on the tram right now.

Dopo means after, and it is followed here by the noun phrase la lezione (the lesson/class).

So:

• dopo la lezione = after the lesson / after class

This is a very common pattern:

• dopo il lavoro = after work
• dopo la cena = after dinner
• dopo il film = after the film

Italian uses the article here because lezione is a noun: la lezione.

Yes. In many contexts, lezione can mean:

• lesson
• class

So Dopo la lezione may be understood as:

• after the lesson
• after class

The exact English translation depends on context.

The comma separates the introductory time phrase from the main part of the sentence:

• Dopo la lezione, torno a casa in tram.

It helps readability, much like in English:
After the lesson, I go home by tram.

In Italian, this comma is common and natural, especially in writing, though short introductory phrases are sometimes written without it as well.

The basic sentence is:

• Dopo la lezione, torno a casa in tram.

But Italian word order is fairly flexible, especially when the meaning is already clear. For example, you might also hear:

• Torno a casa in tram dopo la lezione.
• In tram torno a casa dopo la lezione.

These versions are possible, but the original is the most neutral and natural if you want to start with the time phrase.

Tram is pronounced much like the English word tram.

It is also usually unchanged in the plural:

• il tram = the tram
• i tram = the trams

So it behaves like many short borrowed or indeclinable nouns in Italian.