El teu passaport és a la bossa, però el meu és sobre la taula.

Because in normal Catalan, a possessive usually comes with a definite article:

• el teu passaport = your passport
• la meva casa = my house
• els seus llibres = his/her/their books

So the usual pattern is:

article + possessive + noun

This is different from English, where you normally say just your passport without the.

Because the noun is understood from the first part.

• el teu passaport = your passport
• el meu = mine / my one / my passport

Catalan often leaves out the noun when it is already obvious. In this sentence, el meu means my passport.

This is very natural and common:

• La meva és aquí. = Mine is here.
• Els teus són nous. = Yours are new.

Because they agree with the noun passaport, which is masculine singular.

So you get:

• el teu passaport
• el meu

If the noun were feminine singular, you would use la:

• la teva bossa
• la meva

If it were plural:

• els teus llibres
• les meves claus

So the article tells you the gender and number of the noun, even when the noun is omitted.

In standard Catalan, ser is very commonly used to say where something is located:

• El passaport és a la bossa.
• El llibre és sobre la taula.

For English speakers, this can feel unusual because English uses to be for location without making a distinction, while Catalan has both ser and estar.

A simple learner-friendly rule is:

• use ser for neutral location, especially of objects
• estar is often used in other contexts, sometimes to stress a state, condition, or result

So in this sentence, és is the normal choice.

They express different kinds of location.

• a la bossa here means in the bag
• sobre la taula means on the table or more literally on top of the table

A useful thing to remember is that a in Catalan can cover meanings that English expresses with in, at, or sometimes on, depending on context.

So:

• és a la bossa = it is in the bag
• és a casa = it is at home
• és a l’escola = it is at school

Meanwhile, sobre is more specific and means on / on top of / over.

Because each clause has its own verb.

The structure is:

• El teu passaport és a la bossa
• però el meu és sobre la taula

Even though English sometimes feels compact, Catalan normally keeps the verb in both parts. Leaving out the second és would sound incomplete here.

Yes. Però means but and it works very much like English but to contrast two ideas.

Here it contrasts the locations of the two passports:

• your passport is in the bag
• but mine is on the table

So però is a very common coordinating conjunction.

The accent distinguishes és from es.

• és = is
• es = a reflexive pronoun, like himself/herself/itself in some contexts, or part of reflexive verbs

So the accent helps show that és is the verb form of ser.

Because Catalan only contracts a + el into al.

So:

• a + el → al
• de + el → del

But with la, there is no contraction:

• a la bossa
• de la taula

So if the noun were masculine singular, you might see:

• al cotxe = a + el cotxe

But here bossa and taula are feminine, so you get:

• a la bossa
• sobre la taula

They must agree with the noun they describe.

For teu:

• el teu passaport = your passport
• la teva bossa = your bag
• els teus llibres = your books
• les teves claus = your keys

For meu:

• el meu passaport = my passport
• la meva bossa = my bag
• els meus llibres = my books
• les meves claus = my keys

So in this sentence, teu and meu are masculine singular because passaport is masculine singular.