La professora vol que llegim la lliçó abans.

Because Catalan usually uses que to introduce a subordinate clause after verbs like voler when one person wants another person to do something.

So the structure is:

• La professora vol que...
• literally: The teacher wants that...

In English, that is often optional, but in Catalan que is normally required here.

Because the subject changes.

• La professora vol llegir... = the teacher wants to read...
• La professora vol que llegim... = the teacher wants us to read...

When the person who wants something and the person who does the action are different, Catalan commonly uses:

• voler + que + subjunctive

So llegim is used instead of the infinitive llegir.

In this sentence, it is present subjunctive.

A tricky point is that for nosaltres, the form llegim looks the same in both the present indicative and the present subjunctive. So you identify it by context.

Here, vol que triggers the subjunctive, so llegim must be understood as subjunctive.

Because Catalan often drops subject pronouns when the verb ending already makes the subject clear.

• llegim already means we read / we should read in context

So que llegim is normally enough. You could say que nosaltres llegim, but that would usually add emphasis or contrast, not just neutral information.

Catalan uses definite articles very naturally with specific nouns, including direct objects.

Here, la lliçó means the lesson, probably a particular lesson already known in the context. Using the article is completely normal.

Also notice:

• la agrees with lliçó, which is a feminine noun

Here abans means something like beforehand, earlier, or in advance.

So the idea is that the teacher wants the reading to happen before some understood moment.

At the end of the sentence, abans works on its own. That is different from abans de, which must be followed by a noun or an infinitive:

• abans de classe = before class
• abans de llegir = before reading

But in your sentence, abans stands alone, so it means beforehand rather than before + something explicitly stated.

Yes, Catalan has some flexibility in word order, but the given sentence is a very natural neutral order.

• La professora vol que llegim la lliçó abans.

Putting abans at the end sounds natural if you mean beforehand.

If you move things around, the sentence can still be grammatical, but the emphasis may change, and sometimes it can sound less natural or more context-dependent.

Vol is the third-person singular present indicative of voler.

So:

• jo vull = I want
• tu vols = you want
• ell/ella vol = he/she wants

Here la professora is singular, so the verb is vol.

A few useful pronunciation points:

• ll in Catalan is traditionally a palatal sound, similar to the sound in the middle of English million for many learners
• ç is pronounced like s
• the accent on ó shows that the stress falls on the last syllable

So lliçó is pronounced approximately like lyi-SO.

Because it refers to a female teacher.

Catalan marks grammatical gender on nouns and articles:

• el professor = the male teacher
• la professora = the female teacher

So la professora is feminine both in the article la and in the noun ending -a.