Prima che i bambini entrino in cucina, nascondo lo strofinaccio sporco e pulisco il pavimento.

Because prima che normally requires the subjunctive in Italian.

• entrano = present indicative
• entrino = present subjunctive

So:

• Prima che i bambini entrino in cucina = Before the children go into the kitchen

Italian uses the subjunctive here because the action after prima che is seen as something not yet realized at that moment.

Use prima che when it is followed by a full clause with its own subject and verb.

Here you have:

• i bambini = subject
• entrino = verb

So prima che i bambini entrino is correct.

Use prima di when it is followed by:

• a noun: prima di cena
• an infinitive: prima di entrare

A useful comparison:

• Prima che i bambini entrino, pulisco il pavimento.
  = Before the children come in, I clean the floor.
• Prima di entrare, pulisco il pavimento.
  = Before entering, I clean the floor.

In the second example, the subject of entrare is understood to be the same as the subject of the main verb.

Italian often uses the present tense where English might also use the present, or sometimes a future-like meaning depending on context.

Here the present can express:

• a habitual action: Whenever this situation happens, I hide... and clean...
• an immediate or planned action: Before they come in, I hide... and clean...

So the present tense sounds perfectly natural.

Because bambini begins with a normal consonant sound, b.

For masculine plural nouns:

• i is used before most consonants: i bambini, i libri
• gli is used before vowels, z, s + consonant, gn, ps, x, etc.: gli amici, gli studenti

So:

• singular: il bambino
• plural: i bambini

With entrare, Italian normally uses in for going into a place:

• entrare in cucina
• entrare in casa
• entrare in ufficio

So entrare in cucina means to go into the kitchen.

You may also hear entrare nella cucina, but that is more specific, like into the kitchen as a particular room. In many everyday sentences, in cucina is the most natural choice.

Strofinaccio usually means a dishcloth, tea towel, or kitchen cloth.

It is a masculine noun:

• lo strofinaccio
• gli strofinacci

In this sentence, it is the dirty cloth being hidden before the children come into the kitchen.

Because strofinaccio begins with s + consonant (str-), which takes lo in the singular masculine form.

Compare:

• il pavimento
• lo strofinaccio
• lo studente
• lo zaino

And in the plural:

• gli strofinacci
• gli studenti

So lo strofinaccio is correct because of the sound at the beginning of the word.

In Italian, many descriptive adjectives commonly come after the noun.

So:

• lo strofinaccio sporco = the dirty dishcloth
• il pavimento pulito = the clean floor

This is the most neutral, standard order.

Sometimes adjectives can come before the noun, but that often changes the tone or emphasis. Here, strofinaccio sporco is the normal choice.

The adjective must agree with the noun it describes.

Strofinaccio is:

• masculine
• singular

So the adjective must also be masculine singular:

• sporco

Agreement patterns:

• masculine singular: sporco
• feminine singular: sporca
• masculine plural: sporchi
• feminine plural: sporche

So:

• lo strofinaccio sporco
• la tovaglia sporca
• i piatti sporchi
• le mani sporche

Because pulire is an -ire verb that uses -isc- in some present-tense forms.

Present tense of pulire:

• io pulisco
• tu pulisci
• lui/lei pulisce
• noi puliamo
• voi pulite
• loro puliscono

Many common -ire verbs behave like this, for example:

• capire → capisco
• finire → finisco
• preferire → preferisco

So pulisco il pavimento means I clean the floor.

Because the sentence starts with a subordinate clause:

• Prima che i bambini entrino in cucina

Then it moves to the main clause:

• nascondo lo strofinaccio sporco e pulisco il pavimento

In Italian, as in English, it is very common to separate an introductory clause like this with a comma.

Yes. Italian allows some flexibility.

For example, you could also say:

• Nascondo lo strofinaccio sporco e pulisco il pavimento prima che i bambini entrino in cucina.

This means the same thing.

The original version puts the time condition first, which helps frame the action: Before the children come in...

Literally, nascondo means I hide.

In this sentence it means I put the dirty dishcloth out of sight. So it is not just abstract hiding; it is a very practical, everyday action.

The verb is:

• nascondere = to hide
• nascondo = I hide

Italian uses the definite article much more often than English.

So where English often says:

• I clean the floor

Italian normally says:

• pulisco il pavimento

The same thing happens with many nouns in general statements or everyday actions. Leaving out the article here would usually sound unnatural.

Yes, but the meaning would change slightly.

• bambini = children / little kids
• ragazzi = kids / teenagers / young people, depending on context
• figli = sons/children of the speaker or family being discussed

So i bambini is the best choice if you mean children in a general sense, especially younger ones.