La katalogo enhavas librojn el la tuta mondo.

Because librojn is both:

• plural: -j
• direct object: -n

The base word is libro = book.

So:

• libro = book
• libroj = books
• libron = a/the book as a direct object
• librojn = books as a direct object

In this sentence, la katalogo is doing the action, and librojn is what it contains, so librojn takes the accusative -n.

Because la katalogo is the subject of the sentence, not the direct object.

In Esperanto, the word with -n is usually the direct object, the thing directly affected by the verb. Here:

• La katalogo = the catalog, the thing doing the containing
• enhavas = contains
• librojn = books, the thing being contained

So only librojn gets -n.

Enhavas comes from:

• en = in
• havi = to have

So enhavi literally suggests something like to have in, which is used in Esperanto for to contain.

The ending -as marks the present tense:

• enhavi = to contain
• enhavas = contains / is containing

So La katalogo enhavas... means The catalog contains...

La is the definite article, meaning the.

In la katalogo, it works just like English the catalog.

In la tuta mondo, it means the whole world. Esperanto often uses la in expressions like this where English also normally uses the.

So:

• la katalogo = the catalog
• la tuta mondo = the whole world

Because el means out of, from inside, or more generally from among/from in the sense of origin or source.

Here, librojn el la tuta mondo means books from all over the world or literally books out of the whole world.

De often means of, from, or by, but it is used in different situations, such as:

• possession: la libro de Maria = Maria’s book
• source or authorship in some contexts
• separation from something in other contexts

For places of origin, el is very common:

• Mi venas el Usono = I come from the USA

So el la tuta mondo is the natural choice here.

Tuta means whole or entire.

So:

• mondo = world
• la mondo = the world
• la tuta mondo = the whole world / the entire world

Notice that tuta agrees with the noun:

• both are singular
• neither has -n here

If the noun were plural, the adjective would also be plural:

• la tutaj libroj = all the books / the whole set of books

Because mondo is not in the accusative here.

In Esperanto, adjectives agree with the nouns they describe in:

• number
• case

So if the noun had -n, the adjective would too.

Here we have:

• la tuta mondo

not:

• la tutan mondon

Why? Because this phrase comes after the preposition el, and prepositions normally take their complement without -n.

So both words stay without -n:

• tuta
• mondo

It is best understood as a prepositional phrase modifying librojn.

It tells you what kind of books or which books:

• books from the whole world

So in practice, it works a lot like an adjective phrase in English:

• books from the whole world

But grammatically in Esperanto, it is a prepositional phrase:

• el
  • noun phrase

Yes. That is a very natural English translation.

Even though la tuta mondo is literally the whole world, the most natural English rendering in this sentence is often:

• from all over the world

That is a translation choice, not a change in Esperanto grammar.

Katalogo is the normal Esperanto word.

It is a regular noun:

• katalogo = catalog
• katalogoj = catalogs

Esperanto often adapts international words into its regular spelling and noun ending system, so catalog becomes katalogo.

The normal word order is:

• La katalogo = subject
• enhavas = verb
• librojn = object
• el la tuta mondo = modifying phrase

So this is a standard subject–verb–object sentence.

Esperanto word order is fairly flexible because the -n ending helps show what the object is. So other orders are possible for emphasis, but this version is the most straightforward and natural for a learner.

Because semantically it makes most sense as describing the books:

• books from the whole world

The catalog is not containing from the whole world; rather, the books are from there.

So the phrase is understood as attached to librojn. This is very similar to English:

• The catalog contains books from the whole world

There too, from the whole world describes books.

It might be understandable, but enhavas is better.

Havi means to have, while enhavi specifically means to contain. A catalog does not really have books in the ordinary ownership sense; it contains them as entries or items listed in it.

So La katalogo enhavas librojn... is the more precise and natural choice.