Tutti battono le mani quando l’attore principale entra in scena.

Tutti means everyone or all people here.

It is the masculine plural form, but in Italian it can also be used for a mixed group of people, just like masculine plural often works in Italian. So:

• Tutti battono le mani = Everyone claps / Everybody claps

If the group were all female, you could also hear tutte, but tutti is the normal broad form when talking about people in general.

Because tutti is grammatically plural, the verb has to be plural too.

The verb is battere = to beat / to clap / to strike.

Present tense:

• io batto = I beat / I clap
• tu batti = you beat / you clap
• lui/lei batte = he/she beats
• loro battono = they beat / they clap

Since tutti refers to all people / everyone, Italian treats it like a plural subject, so:

• Tutti battono = Everyone claps

English uses everyone claps with a singular-looking verb, but Italian uses the plural idea: all people clap.

In Italian, battere le mani is the normal expression for to clap.

Literally, it means to beat the hands, but idiomatically it means to clap.

So:

• battere le mani = to clap
• Tutti battono le mani = Everyone claps

This is very natural Italian. Even though English often uses a single verb (clap), Italian commonly uses this full expression.

Italian often uses the definite article with body parts, where English might not.

So:

• le mani = the hands

Even though English says clap your hands or simply clap, Italian naturally says battere le mani.

This use of the article with body parts is very common in Italian:

• Mi lavo le mani = I wash my hands
• Alza la testa = Raise your head

So le mani is completely normal here.

Quando means when.

It introduces the time clause:

• quando l’attore principale entra in scena
  = when the main actor enters/comes on stage

So the sentence is structured like this:

• Tutti battono le mani = main clause
• quando l’attore principale entra in scena = time clause

Italian uses quando very much like English when.

Because il becomes l’ before a masculine singular noun beginning with a vowel.

So:

• il ragazzo
• but l’attore

This is called elision.

Other examples:

• l’amico
• l’insegnante
• l’uomo

So l’attore principale means the main actor.

Principale means main, principal, or leading.

So:

• l’attore principale = the main actor / the lead actor

In Italian, many adjectives often come after the noun, unlike in English. So while English says:

• the main actor

Italian says:

• the actor main literally, but naturally: the main actor

Some adjectives can come before or after depending on style or meaning, but attore principale is the normal order here.

Entrare in scena is a common expression meaning:

• to enter the stage
• to come on stage
• to make an entrance

Literally:

• entra = enters
• in scena = into the scene / onto the stage

In theater vocabulary, entrare in scena is the normal way to say that an actor appears on stage.

So:

• quando l’attore principale entra in scena = when the main actor comes on stage

Yes. The present tense in Italian is often used for:

• actions happening now
• habitual actions
• general truths
• vivid narration

Here, entra and battono are both in the present tense, and the sentence most naturally describes a habitual or typical event:

• Everyone claps when the main actor comes on stage

It is not necessarily about one specific performance happening right now. It can describe what generally happens.

Yes, that is a very natural translation.

Depending on context, possible English versions include:

• Everyone claps when the main actor comes on stage.
• Everybody applauds when the lead actor enters the stage.
• Everyone applauds when the principal actor appears on stage.

The Italian sentence itself is straightforward and natural, and English translation may vary a little depending on style.

This word order is the most neutral and natural:

• Tutti battono le mani quando l’attore principale entra in scena.

But Italian does allow some flexibility. For example, you could move the quando clause to the front:

• Quando l’attore principale entra in scena, tutti battono le mani.

This means the same thing:

• When the main actor comes on stage, everyone claps.

So the order can change for emphasis or style, but the original sentence is perfectly standard.