Il poliziotto è armato.

Il is the masculine singular definite article, so it corresponds to the in English.

• il poliziotto = the police officer / the policeman

If you wanted a police officer, you would use un:

• Un poliziotto è armato.

Italian uses lo only before certain sound patterns, such as:

• z: lo zio
• s + consonant: lo studente
• gn: lo gnomo
• ps: lo psicologo
• x, y, and a few others

Since poliziotto begins with a normal p sound followed by a vowel, it takes il, not lo:

• il poliziotto

The accent is required because è is the verb is.

It helps distinguish it from e, which means and.

• è = is
• e = and

So in this sentence, è armato means is armed, not and armed.

È is the third-person singular of essere, meaning to be.

The sentence follows a very common Italian pattern:

• noun + essere + adjective

Here:

• Il poliziotto = subject
• è = is
• armato = adjective describing the subject

So grammatically it works just like English The police officer is armed.

Here armato is being used as an adjective meaning armed.

It comes from the verb armare (to arm), so it is historically a past participle, but in this sentence you can think of it simply as an adjective describing the police officer's condition.

So:

• è armato = is armed

Because poliziotto is masculine singular, and the adjective must agree with it.

Italian adjectives often change form to match gender and number:

• masculine singular: armato
• feminine singular: armata
• masculine plural: armati
• feminine plural: armate

Since il poliziotto is masculine singular, armato is the correct form.

You would change both the noun and the adjective to feminine:

• La poliziotta è armata.

Changes:

• il → la
• poliziotto → poliziotta
• armato → armata

For masculine plural:

• I poliziotti sono armati.

For feminine plural:

• Le poliziotte sono armate.

Notice that both the verb and the adjective change:

• è → sono
• armato/armata → armati/armate

Not necessarily. Armato means armed, so it means the person has a weapon, but it does not specify which kind.

Depending on context, it could mean armed with:

• a gun
• a knife
• another weapon

If you want to be specific, Italian would say so directly, for example:

• Il poliziotto è armato di pistola. = The police officer is armed with a pistol.

Yes. In that case, it describes the noun directly rather than coming after essere.

• un poliziotto armato = an armed police officer
• il poliziotto armato = the armed police officer

Compare:

• Il poliziotto è armato. = The police officer is armed.
• Il poliziotto armato = the armed police officer

Both are correct, but they do slightly different jobs in the sentence.

A simple English-friendly approximation is:

eel po-lee-TSEE-OT-to eh ar-MA-to

A few useful pronunciation points:

• il sounds roughly like eel
• zi in poliziotto sounds like tsee
• the stress in poliziotto falls on -ot-
• è is a clear eh
• armato is stressed on ma: ar-MA-to

If you want to sound more natural, make the double tt in poliziotto a little longer than a single t.