Видимо, поезд задерживается.

Here видимо means apparently, evidently, or it seems.

It shows that the speaker is making a conclusion from what they observe, not stating a confirmed fact. So the feeling is something like: From what I can tell, the train is delayed.

It is often a little more evidence-based than наверное (probably).

Because видимо is being used as an introductory word (a parenthetical comment by the speaker).

In Russian, introductory words are usually set off by commas:

• Видимо, поезд задерживается.
• Поезд, видимо, задерживается.

If видимо were used in its more literal sense of visibly, it would not be introductory and normally would not take commas. But that is not the meaning here.

Russian has no articles, so there is no separate word for the or a/an.

So поезд can mean:

• a train
• the train

Context tells you which one is meant. In this sentence, it will usually be understood as the train, because the speaker probably has a specific train in mind.

Поезд is in the nominative singular, which is the normal form used for the subject of the sentence.

In Видимо, поезд задерживается, the train is the thing being talked about, so it is the subject:

• поезд = subject
• задерживается = verb

This is also the dictionary form of the noun.

Задерживается comes from задерживаться, related to задерживать (to delay, to hold up).

The ending -ся often gives a verb a reflexive, middle, or passive-like meaning. Here it does not mean the train is literally delaying itself. Instead, it gives the sense:

• is being delayed
• is delayed
• is getting held up

So поезд задерживается is a very natural Russian way to say that the train is delayed.

Russian often uses the present tense imperfective to describe a situation that is happening now or unfolding now.

So задерживается does not mean a timeless general fact here. It means something like:

• is being delayed
• seems to be delayed
• is apparently delayed right now

This is a normal way to talk about a current travel disruption.

Formally, it is a reflexive verb because it has -ся. But in meaning, it is often best understood as middle/passive-like.

So in this sentence, the best English interpretation is not the train delays itself, but rather:

• the train is delayed
• the train is being delayed

Russian often uses -ся verbs this way, where English would prefer a passive construction.

These are close, but not identical:

• поезд задерживается = the train is delayed / is being delayed
  Focuses on the delay itself, often due to external circumstances.

• поезд опаздывает = the train is late
  A more general idea: it is not on time.

• поезд задержан = the train has been delayed / the train is delayed
  More formal, often used in announcements; it sounds more like a stated result.

So задерживается is a very natural everyday way to describe an ongoing delay.

Yes. Russian word order is flexible.

These are all possible, with slightly different emphasis:

• Видимо, поезд задерживается. — neutral
• Поезд, видимо, задерживается. — also very natural; puts train first as the topic
• Задерживается, видимо, поезд. — much more marked; used for special emphasis or style

So the original sentence is a neutral, standard way to say it.

The stress is:

• ви́димо
• по́езд
• заде́рживается

A rough pronunciation guide:

• ви́димо ≈ VEE-di-ma
• по́езд ≈ PO-yezd
• заде́рживается ≈ za-DYER-zhi-va-yet-sa

Stress matters in Russian, so it is worth learning these with the stress included.