Learn Hardcore Russian: На конференцию приедут докладчики и участники из разных городов. - Speakers and participants from different cities will come to the conference.

The preposition в is more for being inside a physical space: в комнате (in the room), в магазине (in the shop), в университете (in/at the university as a place).

A конференция is treated as an event you go to (like a concert), so the natural choice is на конференцию, not в конференцию.

What case is конференцию in, and why is that case used?

Конференцию is accusative singular feminine.

Pattern:

nominative: конференция
accusative: конференцию

After на you get:

на конференции (prepositional) = at the conference (location, no movement)
на конференцию (accusative) = to the conference (direction/movement)

In this sentence there is movement towards the conference (people will arrive there), so на takes the accusative: на конференцию.

Could the sentence start with Докладчики и участники instead of На конференцию? Does the word order change the meaning?

Yes, you can say:

Докладчики и участники из разных городов приедут на конференцию.
На конференцию приедут докладчики и участники из разных городов.

Both are grammatically correct and mean the same in basic content.

The difference is in emphasis:

Starting with Докладчики и участники… emphasizes who is coming.
Starting with На конференцию… emphasizes where they are coming to (the event itself).

Russian word order is relatively flexible; moving elements around often changes what is highlighted, not the core meaning.

What exactly does приедут mean, and which verb is it from?

Приедут is:

3rd person plural
future tense
perfective aspect
from the verb приехать (to arrive, to come by vehicle).

So приедут = they will arrive / they will come (by vehicle), focusing on the result: their arrival at the conference.

The imperfective partner is приезжать:

приезжать (impf.) ↔ приехать (pf.)

What is the difference between приедут and приезжают in a sentence like this?

Aspect and time:

приедут – perfective future
- one-time, completed future event: will arrive (once, at that time)
- used for planned, scheduled arrivals.
приезжают – imperfective present
- are arriving (right now)
- (they) arrive / come regularly (habitually)
- for repeated or ongoing actions, not a single future event.

To say “Speakers and participants from different cities will come (once) to the conference”, Russian normally uses the perfective future: приедут.
For repeated future actions, you’d use the imperfective, often with будут: будут приезжать (will be coming repeatedly).

Why is it приедут and not придут?

Both mean to come / to arrive, but they differ in how people come:

прийти / приходить – to come on foot, by walking
приехать / приезжать – to come by vehicle / transport, typically from farther away (other cities, regions, countries, etc.)

Since the sentence mentions из разных городов (from different cities), it strongly implies that people are traveling by some transport (car, train, plane).
That’s why приедут is the natural choice here, not придут.

What is the difference between докладчики and участники?

Both refer to people at the conference, but:

докладчики – speakers, presenters
From доклад = a talk, report, presentation. These are the people giving talks.
участники – participants, attendees
Everyone taking part in the conference (listeners, speakers, organizers, etc. can all be участники).

So in this sentence:

докладчики — those who present
участники — all other participants (including possibly some of the speakers)

Sometimes you might also see выступающие or спикеры used for “speakers.”

Why is it из разных городов and not из разные города or от разных городов?

Three points:

The preposition:
- из means from, out of a place: из Москвы (from Moscow), из города (from the city).
- от is more often used for from a person / source / direction: от друга (from a friend), от двери (from the door).
Here we talk about origin from cities, so из is correct: из разных городов.
The case after “из”:
- из always takes the genitive case.
- Plural genitive of город is городов; plural genitive of разный is разных.
- So we must say из разных городов (both words in genitive plural).
*из разные города is wrong because разные города is nominative/accusative plural, not genitive.
Meaning:
- из разных городов = from different cities (they come from various cities).

What case is городов in, and how is its plural formed?

Городов is genitive plural of город (city).

Singular:

nominative: город
genitive: города
dative: городу
accusative: город
instrumental: городом
prepositional: в городе

Plural:

nominative: города
genitive: городов
dative: городам
accusative: города
instrumental: городами
prepositional: в городах

In из разных городов, the preposition из requires the genitive plural, so we get городов.

Could we say На конференции будут докладчики и участники из разных городов instead? How would that differ?

Yes, that sentence is also correct, but the nuance changes:

На конференцию приедут докладчики и участники…
Focuses on the arrival: they will come to the conference.
На конференции будут докладчики и участники…
Focuses on their presence: there will be speakers and participants at the conference (says nothing about how/when they arrive).

Both are fine; you choose based on whether you want to highlight the event of arriving (приедут) or the fact of being present (будут).

How are the main words in the sentence stressed and pronounced?

Approximate stresses (stressed syllable in capitals; transcription in brackets):

на конфере́нцию – na kon-fe-REN-tsi-yu
(конфере́нцию: kon-fe-REN-tsi-yu)
при́едут – pri-YE-dut
докла́дчики – da-KLAD-chi-ki
уча́стники – u-CHAST-ni-ki
и́з – IZ
ра́зных – RAZ-nykh
городо́в – ga-ra-DOV

Knowing where the stress falls is important in Russian, because it often changes both pronunciation and sometimes even meaning.

Why isn’t there a comma before и участники?

In Russian, when you have a simple list of subjects with one shared verb, you don’t separate them with a comma:

докладчики и участники приедут…

It’s the same pattern as in English:

“Speakers and participants will come…” – no comma.

You would use a comma only in longer or more complex lists, or if there were additional structures requiring it. Here, докладчики и участники is just a normal pair joined by и, so no comma is needed.

Is there any difference between разных and различных in из разных городов?

Both разных and различных can mean different / various, and in this sentence they are very close in meaning:

из разных городов – from different cities (neutral, very common)
из различных городов – from various cities (a bit more formal or bookish)

In everyday speech, разных is more natural here. Различных might sound slightly more official or stylistically elevated, but grammatically both are correct.