O oleiro trabalha na oficina.

O is the masculine singular definite article, meaning the.

It matches oleiro, which is a masculine singular noun:

• o oleiro = the potter

In Portuguese, articles are used more often than in English, so O oleiro sounds natural where English simply says The potter.

Oleiro means potter, a person who makes things out of clay, especially pottery.

It is a masculine noun. The feminine form is usually oleira:

• o oleiro = the male potter
• a oleira = the female potter

Trabalha is the 3rd person singular present tense of the verb trabalhar (to work).

That form is used because the subject is O oleiro = he / the potter.

Here are the relevant forms:

• eu trabalho = I work
• tu trabalhas = you work
• ele/ela trabalha = he/she works

So:

• O oleiro trabalha = The potter works

Na is a contraction of em + a:

• em = in / at
• a = the

So:

• na oficina = in the workshop / at the workshop

This kind of contraction is very common in Portuguese:

• em + o = no
• em + a = na
• em + os = nos
• em + as = nas

Because Portuguese normally uses the article here.

So instead of saying just in workshop, Portuguese says in the workshop:

• na oficina

This is one of the big differences from English: Portuguese often includes articles where English may not.

Here, oficina means workshop, the place where the potter works.

Depending on context, oficina can also mean:

• repair shop
• garage
• workshop in a crafts or manual-work sense

In this sentence, because the subject is oleiro, the meaning workshop is the most natural one.

Yes. The order is the standard Portuguese pattern:

Subject + verb + place

• O oleiro = subject
• trabalha = verb
• na oficina = place

So it is a very straightforward sentence.

Yes. Portuguese often allows the subject to be omitted when it is clear from the verb form.

So Trabalha na oficina is grammatically possible, but it usually means:

• He/She works in the workshop

If you specifically want to say the potter, keeping O oleiro makes that explicit.

A rough English-friendly approximation is:

oh-LAY-roo

But in European Portuguese, the final o is often reduced, so it may sound closer to: oh-LAY-ru

Also:

• ei sounds like ay in say
• the r in the middle is a tapped r

A rough approximation is:

u uh-LAY-ru truh-BAI-lya nuh oh-fee-SEE-nuh

A few useful notes:

• O often sounds close to u
• trabalha contains lh, which sounds like the lli in million
• na is usually a short unstressed syllable
• European Portuguese often reduces unstressed vowels quite a lot

Lh is a special Portuguese sound. It is pronounced like the lli in million or the li in some pronunciations of brilliant.

So trabalha is not pronounced like trabala. The ending is more like:

• -balha

This sound also appears in words such as:

• filho = son
• mulher = woman
• trabalho = work

Yes, but it means something slightly different.

• O oleiro trabalha na oficina = The potter works in the workshop.
  This describes his work or usual place of work.

• O oleiro está na oficina = The potter is in the workshop.
  This tells you where he is at the moment.

So trabalha talks about working, while está talks about location or temporary state.

You would change the article, noun, and verb:

• O oleiro trabalha na oficina.
• Os oleiros trabalham na oficina.

So:

• o → os
• oleiro → oleiros
• trabalha → trabalham

That means:

• The potters work in the workshop.

It is a real and correct word, but it is not as common as more everyday job words like professor, médico, or empregado.

A learner may not see oleiro very often unless the topic is:

• crafts
• pottery
• traditional occupations
• rural life
• history or culture

Still, it is a useful word and perfectly natural.