Learn Hardcore Russian: Молодой артист выходит на сцену и берёт микрофон. - A young performer walks onto the stage and takes the microphone.

арти́ст is a masculine, singular noun in the nominative case (it is the subject).
The matching adjective form is молодо́й (masculine, singular, nominative).

Other forms would be for different genders:

молода́я – feminine (for example: молода́я де́вушка – a young girl)
молодо́е – neuter (for example: молодо́е де́рево – a young tree)

So with арти́ст, you must use молодо́й арти́ст.

What exactly does арти́ст mean? Is it the same as English “artist”?

Арти́ст is a false friend for English speakers.

In Russian, арти́ст usually means a performer: an actor, singer, dancer, circus performer, etc. – someone who performs on a stage.
The usual word for a visual artist (painter, etc.) is худо́жник.

Also:

Masculine: арти́ст
Feminine: арти́стка

So молодо́й арти́ст is best translated as “a young performer” or “a young actor”, not “a young artist” in the painter sense.

What tense and aspect is выхо́дит, and can it describe a single action?

Выхо́дит is:

Present tense
3rd person singular
Imperfective aspect
From the verb выходи́ть (to go out, to come out, to step out onto something)

Even though it is imperfective, it can absolutely describe a single, one-time action in a narrative:

Молодо́й арти́ст выхо́дит на сце́ну…
= “The young performer comes out onto the stage…”

Russian often uses the imperfective present to narrate events as if they’re happening right now (like live commentary or vivid storytelling), even if it’s a single event.

Why do we say выхо́дит на сце́ну instead of идёт на сце́ну or прихо́дит на сце́ну?

All three verbs involve movement, but their nuances differ:

выходи́ть на сце́ну – the standard phrase for “to go out onto the stage,” “to step onto the stage,” emphasizing emerging from behind the scenes/curtain into view.
идти́ на сце́ну – literally “to go toward the stage.” This is more neutral and may suggest just moving in that direction, not necessarily the moment of appearing on stage.
приходи́ть на сце́ну – “to come/arrive at the stage,” which sounds odd for the moment of performance; it’s more about arriving somewhere, not stepping out in front of the audience.

For a performer appearing in front of the audience, выходи́ть на сце́ну is the natural, idiomatic choice.

Why is it на сце́ну and not на сце́не?

In Russian, the preposition на can take either:

Accusative (movement onto / to a surface or place)
Prepositional (location on / at a surface or place)

Compare:

Он выхо́дит на сце́ну. – He goes onto the stage. (movement → accusative: сце́ну)
Он стои́т на сце́не. – He stands on the stage. (location → prepositional: сце́не)

In your sentence, there is movement toward the stage, so на сце́ну (accusative) is required.

What case is сце́ну, and how is it formed from сце́на?

Сце́ну is the accusative singular form of сце́на (“stage”).

Сце́на is a feminine noun ending in -а. For such nouns:

Nominative singular: сце́на (subject form)
Accusative singular: сце́ну (used here after на with motion)

Pattern for many feminine -а nouns:
-а → -у in the accusative singular when they’re direct objects or when required by prepositions indicating direction (like на, в indicating motion).

How is the whole sentence stressed and roughly pronounced?

Stresses:

Молодо́й – mo-lo-DOY
арти́ст – ar-TEEST
выхо́дит – vy-HO-dit
на сце́ну – na STSE-nu
и – ee
берёт – be-RYOT (ё is always stressed and pronounced “yo”)
микрофо́н – mi-kra-FON

With stress marks in Russian:
Молодо́й арти́ст выхо́дит на сце́ну и берёт микрофо́н.

Note the cluster сц in сце́ну: it’s like saying “stse” quickly, somewhat like “let’s see” run together.

Why is берёт written with ё, and what is the infinitive and conjugation pattern?

The verb is бра́ть – “to take” (imperfective).

Берёт is the 3rd person singular present form of бра́ть:
- я беру́
- ты берёшь
- он/она берёт
- мы берём
- вы берёте
- они́ беру́т

About ё:

ё is always stressed and pronounced “yo”.
In many printed texts, ё is written as е (берет), but it is still pronounced “берёт.”
In learning materials, you often see ё explicitly, as here, to show correct stress and sound.

Why is it берёт and not возьмёт? What is the aspect difference?

Бра́ть / взять is an aspect pair:

бра́ть (imperfective) – process, habitual action, neutral narrative
взять (perfective) – single, completed action as a whole; its “present” forms have future meaning

Forms in the 3rd person singular:

он берёт – he takes / is taking (present, imperfective)
он возьмёт – he will take (future, perfective)

In your sentence, we are describing the scene as happening now (narrative present), so we use берёт.

If you said:

…и возьмёт микрофо́н.
it would mean “…and (then) he will take the microphone.” (future), not present.

Which case is микрофо́н in, and why does it look like the dictionary form?

Микрофо́н is in the accusative singular as the direct object of берёт.

For masculine inanimate nouns ending in a consonant, the accusative singular form is identical to the nominative:

Nominative: микрофо́н (as in dictionary)
Accusative: микрофо́н (same form)

So even though the form does not change, its function in the sentence is accusative: it’s the thing being taken.

Can the word order be changed, for example to На сце́ну выхо́дит молодо́й арти́ст и берёт микрофо́н?

Yes. Russian word order is relatively flexible.

Молодо́й арти́ст выхо́дит на сце́ну… – neutral: first you mention who, then what he does.
На сце́ну выхо́дит молодо́й арти́ст… – puts extra emphasis on на сце́ну (the place / direction): onto the stage comes a young performer.

Both are grammatically correct; the choice mostly affects emphasis and stylistic feel, not basic meaning.

Why is there no comma before и in …на сце́ну и берёт микрофо́н?

In Russian, when two verbs share the same subject and are joined by и (“and”), a comma is not usually used:

Молодо́й арти́ст выхо́дит на сце́ну и берёт микрофо́н.
One subject (молодо́й арти́ст), two predicates (выхо́дит, берёт) → no comma before и.

A comma is used with и in other situations (for example, when joining full clauses with their own subjects), but not in this simple “subject + verb and verb” structure.

Could I say Он выхо́дит на сце́ну и берёт микрофо́н instead? Why is он not used here?

You can say:

Он выхо́дит на сце́ну и берёт микрофо́н. – He goes onto the stage and takes the microphone.

However, in the original sentence, the subject is named explicitly as молодо́й арти́ст. In Russian, you don’t normally add a pronoun in the same clause when the noun subject is already there; that would be redundant:

Молодо́й арти́ст он выхо́дит… – sounds unnatural.

So:

Either Молодо́й арти́ст выхо́дит…
Or, if the person has been previously mentioned and you don’t need to specify “young artist” again: Он выхо́дит…

In your sentence, молодо́й арти́ст itself serves as the subject, so он is unnecessary.