Il copertone protegge la camera d'aria.

Il and la are both singular definite articles, meaning the.

• il copertone = the tire
• la camera d'aria = the inner tube

Italian articles change depending on the gender and number of the noun:

• il = masculine singular
• la = feminine singular

So copertone is masculine, while camera is feminine.

Protegge is the third-person singular present tense of proteggere = to protect.

The subject is il copertone, which is singular, so the verb must match it:

• io proteggo = I protect
• tu proteggi = you protect
• lui/lei protegge = he/she/it protects
• noi proteggiamo = we protect
• voi proteggete = you all protect
• loro proteggono = they protect

So Il copertone protegge... means The tire protects...

D'aria is a shortened form of di aria.

In Italian, di often contracts before a word starting with a vowel, especially in fixed expressions:

• di + aria → d'aria

So:

• camera d'aria literally = chamber of air
• natural English equivalent = inner tube

The apostrophe shows that the i in di has been dropped.

Yes. This is a very common thing in vocabulary learning: the literal parts of an Italian expression may not match the usual English word-for-word expression.

• camera = chamber/room
• aria = air
• camera d'aria = inner tube

So even if the literal meaning helps you remember it, you should learn camera d'aria as a set expression.

In standard Italian, la becomes l' before a vowel:

• la amica → l'amica
• la aria → l'aria

But here the noun is camera, which begins with c, not a vowel, so it stays la:

• la camera
• la camera d'aria

Only the second part, d'aria, has an apostrophe because it comes from di aria.

They are related, and in many contexts they can overlap, but they are not always felt in exactly the same way.

• copertone often refers specifically to the outer tire
• pneumatico is a more general or technical word for tire

In a bicycle context, copertone and camera d'aria are often paired, because the outer tire surrounds and protects the inner tube.

So this sentence sounds very natural in that context.

This sentence uses the most basic and neutral Italian word order:

subject + verb + object

• Il copertone = subject
• protegge = verb
• la camera d'aria = direct object

Italian can sometimes move things around for emphasis, but the normal order here is the same as in English. For a learner, this is the best pattern to recognize first.

A useful rough guide is:

pro-TEJ-je

A few points:

• the stress is on -teg-
• gg before e sounds like the j in judge
• so protegge does not have a hard g sound like in go

If you break it up:

• pro
• teg
• ge

But the last two parts flow together with that soft j sound.

Because Italian normally uses articles more regularly than English does. If both nouns are definite, each one usually takes its own article.

So Italian says:

• Il copertone protegge la camera d'aria

English also does this here:

• The tire protects the inner tube

But in other cases, Italian may use an article where English would not, so getting used to articles is very important.

The gender comes from the main noun, which is camera.

Since camera is feminine, the whole expression is feminine:

• la camera d'aria
• una camera d'aria

The second part, d'aria, does not change the gender. In expressions like this, the article agrees with the head noun: here, that is camera.

Yes. Since la camera d'aria is a feminine singular direct object, the direct object pronoun would be la.

So:

• Il copertone protegge la camera d'aria.
• Il copertone la protegge. = The tire protects it.

In natural Italian, object pronouns usually come before the verb.

The dictionary form is copertone, singular masculine.

The ending -one in Italian often suggests something large or big. It is an augmentative ending.

Compare:

• coperta = cover/blanket
• copertone = literally something like big covering

Historically and semantically, that makes sense for a tire: it is the outer covering around the inner tube.

You do not need to analyze it every time, but noticing endings like -one can sometimes help you remember vocabulary.