La bossa on guardo el passaport és al costat de la maleta.

Here on means where or in which. It introduces a relative clause that describes la bossa.

So:

• la bossa = the bag
• on guardo el passaport = where I keep the passport

Together, La bossa on guardo el passaport means the bag where I keep the passport.

Guardo is the first-person singular present form of guardar.

• guardar = to keep, store, put away
• guardo = I keep / I store

The ending -o tells you the subject is I.

Not usually in this kind of sentence. Even though it looks like English guard, guardar very often means to keep, to store, or to put away.

So here:

• guardo el passaport = I keep the passport / I store the passport

If you translated it as I guard the passport, that would sound too literal in most contexts.

Catalan often leaves out subject pronouns because the verb ending already shows who the subject is.

• guardo already means I keep
• jo guardo is possible, but it adds emphasis or contrast

So the sentence does not need jo.

El passaport literally means the passport. In context, it may already be obvious whose passport it is, so Catalan does not always need to say my.

If you want to make ownership explicit, el meu passaport is also possible.

So:

• el passaport = the passport
• el meu passaport = my passport

Both can work, depending on context and emphasis.

Because it is describing which bag. This is a relative clause, and in Catalan it normally comes right after the noun it modifies.

So the structure is:

• La bossa = the bag
• on guardo el passaport = where I keep the passport

This is the same basic idea as English the bag where I keep the passport.

Because on guardo el passaport is essential information: it identifies which bag you mean.

This is called a restrictive relative clause, and restrictive clauses normally do not take commas.

So the meaning is:

• not just any bag
• specifically the bag where I keep the passport

Al costat de means next to, beside, or at the side of.

It is a fixed expression:

• costat = side
• al costat de = at the side of / next to

So:

• és al costat de la maleta = is next to the suitcase

Because al is the normal contraction of a + el in Catalan.

So:

• a + el costat → al costat

This is similar to how some languages combine a preposition and an article into one form.

In Catalan, ser can be used for simple location, especially in neutral descriptions like this one.

So La bossa és al costat de la maleta is natural and correct.

In many contexts, especially in everyday speech, you may also hear està for location:

• La bossa està al costat de la maleta

That can sound a bit more like describing its current position. The exact preference can vary by speaker and region, but és here is completely normal.

In standard Catalan, it is better to say:

• La bossa on guardo el passaport

because on already gives the idea of place, so adding hi is usually unnecessary.

You may hear on hi in some colloquial speech, but if you are learning standard written Catalan, use on by itself here.

• bossa = bag
• maleta = suitcase

So the sentence is talking about a bag that is located next to a suitcase.

Depending on context, bossa can mean different kinds of bag, but maleta is specifically a suitcase or travel case.

You can break it into three parts:

• La bossa = the bag
• on guardo el passaport = where I keep the passport
• és al costat de la maleta = is next to the suitcase

So the full structure is:

• [noun] + [relative clause] + [main verb + location]

That makes the sentence a very useful model for building similar ones, such as:

• La caixa on poso les claus és a l’entrada.
• El calaix on guardo els documents és tancat.