En la salono ni trinkas teon dum la infanoj ludas.

The ending -n marks the direct object in Esperanto.
Here, teon is the thing being drunk, so it takes the accusative ending:

• teo = tea
• teon = tea as the direct object

So ni trinkas teon means we drink tea, with tea as the object of drink.

Esperanto has only one article: la, which means the. It does not have a separate word for a/an.

So:

• la salono = the living room / the lounge
• la infanoj = the children
• teon without la = just tea, often in a general or indefinite sense

If you said la teon, that would mean the tea, referring to specific tea.

Dum means while here. It connects two actions happening at the same time:

• ni trinkas teon
• la infanoj ludas

So dum introduces the second action that is going on simultaneously.

A useful detail: dum can also work like during before a noun, but here it is followed by a whole clause, so it means while.

In Esperanto, -as is the present tense ending.

So:

• trinkas = drink / are drinking
• ludas = play / are playing

Esperanto does not usually make a separate distinction between we drink and we are drinking. The plain present tense -as can cover both, and the context tells you which sense is meant.

The ending -j marks the plural in Esperanto.

• infano = child
• infanoj = children

So la infanoj means the children.

Because Esperanto verbs do not change according to person or number.

In English, we say:

• I play
• she plays

But in Esperanto, the verb form stays the same:

• mi ludas
• ŝi ludas
• ni ludas
• la infanoj ludas

That makes verb conjugation much simpler than in English.

That part gives the setting first: the location.

Esperanto word order is fairly flexible, and speakers often move a phrase to the front to emphasize it or to set the scene. Starting with En la salono is natural because it tells you where the action is happening before the main clause continues.

You could also say:

• Ni trinkas teon en la salono dum la infanoj ludas.

That would still be correct.

En means in or inside. It is used because the people are located inside the room.

So:

• en la salono = in the living room / in the lounge

A learner might compare it with ĉe, but ĉe usually means something more like at, by, or at the place of, not specifically inside. For a room, en is the normal choice when you mean physical location inside it.

Yes. Ludi can be used on its own to mean to play in the general sense.

So la infanoj ludas simply means that the children are playing.

If you want to say what they are playing, you can add more information, for example:

• La infanoj ludas ludon = The children are playing a game
• La infanoj ludas per pilko = The children are playing with a ball

But it is completely normal to leave it as just ludas.

A comma is often optional in a sentence like this.

Esperanto punctuation is generally less rigid than English punctuation in some cases. Since the sentence is clear without a comma, many writers would simply write:

• En la salono ni trinkas teon dum la infanoj ludas.

Some people might also write a comma before dum for readability:

• En la salono ni trinkas teon, dum la infanoj ludas.

Both can be acceptable, but without the comma is very natural here.