La mare em dona una tassa de te.

Because Catalan normally uses the definite article with many family words: la mare (mother / mum), el pare (father / dad), la germana (sister), etc.

So even where English would often just say Mother or my mother, Catalan commonly says la mare.

It can mean either, depending on context.

• la mare can literally mean the mother
• but in everyday speech it often means mum / mother, when it is obvious whose mother is meant

If you want to be completely explicit, you can say:

• la meva mare = my mother

So La mare em dona una tassa de te could naturally mean Mum gives me a cup of tea.

em is the weak pronoun meaning to me or me.

The verb donar works like to give:

• donar una cosa a algú = to give something to someone

So:

• La mare em dona... = Mother gives me...
• literally: Mother gives to me...

The full stressed form would be a mi, but here Catalan normally uses the weak pronoun em.

Because Catalan weak pronouns normally go before a conjugated verb.

So you get:

• em dona = gives me
• et dona = gives you
• li dona = gives him/her

This is normal Catalan word order.

A pronoun can appear after the verb in some other structures, especially with:

• infinitives
• gerunds
• affirmative commands

For example:

• donar-me = to give me
• dona'm = give me

But in your sentence, em dona is exactly what you would expect.

Here dona is the third-person singular present of donar (to give).

So:

• dono = I give
• dones = you give
• dona = he/she gives

In this sentence, dona means gives.

In older spelling, many learners saw dóna for the verb and dona for the noun woman.

In current standard Catalan, this accent is usually not written, so both are spelled dona. Context tells you which one it is.

In this sentence, it is clearly the verb, because it comes after the subject and before the object:

• La mare em dona una tassa de te = Mother gives me a cup of tea

It does not mean woman here.

Because tassa (cup) is a feminine singular noun.

So the article must match it:

• una tassa = a cup
• la tassa = the cup

If the noun were masculine, you would use un instead of una.

This is the normal way to express a container plus its contents:

• una tassa de te = a cup of tea
• un got d'aigua = a glass of water
• una ampolla de vi = a bottle of wine

So de here means of, just like in English.

Because te here is being used as a general substance, not as a specific identified tea.

So Catalan says:

• una tassa de te = a cup of tea

not:

• una tassa del te

You only get del when de + el is needed:

• del = de + el

But here there is no article before te, so it stays simply de te.

Because the noun te (tea) is written without an accent.

This is different from:

• té = has

So:

• te = tea
• té = has

That accent matters.

It is the present tense, and depending on context it can often correspond to either:

• gives
• is giving

So La mare em dona una tassa de te might mean:

• Mother gives me a cup of tea
  or
• Mother is giving me a cup of tea

If you really want to stress an ongoing action, Catalan can also use:

• La mare m'està donant una tassa de te = Mother is giving me a cup of tea

But the simple present is very common and natural.

You can use a mi, but usually not as the normal neutral replacement.

The most natural basic sentence is:

• La mare em dona una tassa de te

If you want emphasis or contrast, you can add a mi:

• A mi, la mare em dona una tassa de te = As for me, Mother gives me a cup of tea
• La mare em dona una tassa de te a mi, no a tu = Mother gives a cup of tea to me, not to you

So:

• em = normal unstressed pronoun
• a mi = stressed/emphatic form

Yes, if the context already makes it clear who is doing the action.

Catalan often leaves out the subject when it is understood:

• Em dona una tassa de te = She gives me a cup of tea / Mum gives me a cup of tea

But including La mare makes the subject explicit. It tells you exactly who is giving the tea.