Из чайника льётся горячая вода.

Because из means out of / from, and it requires the genitive case in Russian.

• dictionary form: чайник = kettle, teapot
• genitive singular: чайника

So:

• из чайника = out of the kettle

This is a very common pattern:

• из дома = out of the house
• из машины = out of the car
• из бутылки = out of the bottle

Because вода is the subject of the sentence: it is the thing that is flowing/pouring.

Russian word order is much freer than English word order. In English, the subject usually has to come before the verb:

• Hot water is pouring from the kettle.

In Russian, the subject can come after the verb without changing its grammatical role:

• Из чайника льётся горячая вода.

Here, горячая вода is still the subject, so it stays in the nominative case.

Because горячая has to agree with вода.

Since вода is:

• feminine
• singular
• nominative

the adjective must also be:

• feminine
• singular
• nominative

So:

• горячая вода = hot water

Compare:

• горячую воду = hot water as a direct object
• горячей воды = of hot water / some hot water

Льётся is the 3rd person singular present tense of литься.

It means something like:

• is pouring
• is flowing
• is running out

It is commonly used for liquids when they move as a stream. In this sentence, it suggests that the hot water is coming out of the kettle in a flowing way.

So the sentence gives the idea:

• Hot water is pouring from the kettle or
• Hot water is flowing out of the kettle

The verb here is литься, not лить.

• лить = to pour something
  
  • example: Он льёт воду в чашку. = He is pouring water into a cup.
• литься = to pour / flow by itself
  
  • example: Вода льётся. = The water is pouring / flowing.

So -ся here does not mean a literal English self. It is just part of the verb that makes it work in this more intransitive sense.

A useful contrast:

• Она льёт чай. = She is pouring tea.
• Чай льётся из чайника. = Tea is pouring from the kettle.

Because its subject, горячая вода, is singular.

Russian verbs in the present tense agree with the subject in number and person.

• вода = singular
• so the verb is льётся = it pours / is pouring

If the subject were plural, the verb would be plural too:

• Из чайника льются капли воды. = Drops of water are coming out of the kettle.

Because Russian word order is flexible, and the beginning of the sentence often shows what the speaker wants to focus on first.

• Из чайника льётся горячая вода.
  Focuses first on where the water is coming from.

• Горячая вода льётся из чайника.
  Feels a bit more neutral from an English-speaking perspective.

Both are grammatical. The original version sounds natural and can emphasize the source: from the kettle.

Sometimes yes, but there is a difference in feel.

• течь / течёт = to flow, run, leak
• литься / льётся = to pour, stream, flow

Льётся often suggests a more noticeable pouring stream.
Течёт can sound more like ordinary flowing or even leaking.

So:

• Из чайника льётся горячая вода. = hot water is pouring out
• Из чайника течёт горячая вода. = hot water is flowing/running out

In many situations both are possible, but льётся is a very good choice when you imagine water pouring.

Льётся is pronounced approximately lyot-sya.

A few key points:

• ё is always stressed
• ль is a soft l
• ться / тся in this form sounds like ца in normal speech

So it sounds roughly like:

• ЛЬЁ-тся → LYOT-sa

The letter ё matters because it shows both the pronunciation and the stress. If you wrote льется without the dots, a learner might not know where the stress goes.

Russian has no articles.

So вода can mean:

• water
• the water
• sometimes some water

The exact meaning depends on context.

In this sentence, English would normally say:

• Hot water is pouring from the kettle or
• The hot water is pouring from the kettle

Russian does not need a separate word for that.

Чайник most often means kettle, especially in everyday modern usage.

Depending on context, it can sometimes refer to a vessel for tea, but in a sentence like:

• Из чайника льётся горячая вода

the natural meaning is kettle, because hot water is pouring from it.

So for a learner, kettle is the best interpretation here.

Usually, the normal order is:

• горячая вода

That is the standard adjective + noun order.

You may sometimes see adjective placement changed in poetry, stylistic language, or for special emphasis, but in ordinary speech and writing, горячая вода is the natural choice.

So this sentence uses the most normal order.

Usually it sounds like something currently happening or something visually observable:

• Hot water is pouring from the kettle.

Russian present tense often covers both simple present and present continuous meanings, depending on context.

So льётся can mean:

• pours
• is pouring

In this sentence, most learners should understand it as is pouring / is flowing out.