Mi iras rekte al la stacidomo.

In Esperanto, verbs always take an ending that shows the tense or mood.

Here, iras = go / am going because -as is the present tense ending.

So:

• mi iras = I go / I am going
• mi iris = I went
• mi iros = I will go
• mi iru = go! / should go
• mi irus = would go

The verb itself is iri = to go.

It can mean either, depending on context.

Esperanto present tense -as does not force a distinction between:

• I go
• I am going

So Mi iras rekte al la stacidomo can be understood as:

• I go straight to the train station, or
• I am going straight to the train station

Usually the situation makes it clear.

Rekte is an adverb, and adverbs in Esperanto usually end in -e.

So:

• rekta = direct, straight (adjective)
• rekte = directly, straight (adverb)

In this sentence, rekte describes the action iras:

• Mi iras rekte = I am going straight / directly

That is why it uses -e, not -a.

Al means to, toward and shows direction by itself, so you do not need the accusative -n after it.

• al la stacidomo = to the station

By contrast, Esperanto can also show movement into something with en plus -n:

• en la stacidomon = into the station

So the difference is:

• al la stacidomo = toward/to the station
• en la stacidomon = into the station

In your sentence, the idea is simply going to the station, so al is the normal choice.

Because it follows the preposition al.

Normally, Esperanto marks the direct object with -n, but stacidomo here is not a direct object. It is part of the prepositional phrase al la stacidomo.

So:

• Mi vidas la stacidomon = I see the station
  (stacidomon gets -n because it is the direct object)
• Mi iras al la stacidomo = I go to the station
  (no -n, because al already shows the role)

La is the definite article, meaning the.

So:

• stacidomo = a train station / train station
• la stacidomo = the train station

Esperanto has only one article, la, and it does not change for gender, number, or case.

In this sentence, la shows that a specific station is meant.

It is one compound word, and Esperanto makes compounds very often.

stacidomo can be understood as:

• staci- from stacio = station
• domo = building, house

So stacidomo literally suggests something like station-building, and in normal usage it means railway station / train station.

This kind of word-building is very common in Esperanto.

Yes, Esperanto word order is fairly flexible.

All of these are possible:

• Mi iras rekte al la stacidomo
• Mi rekte iras al la stacidomo
• Rekte mi iras al la stacidomo

However, they may sound slightly different in emphasis.

The version Mi iras rekte al la stacidomo is very natural and neutral. It places the adverb close to the movement toward the station.

Yes, it can suggest either idea depending on context.

Rekte often means:

• straight
• directly
• without detouring
• sometimes right away, depending on context

In this sentence, native English speakers will often understand it as:

• going by a direct route, or
• heading straight there instead of somewhere else first

Context decides the exact shade of meaning.

A simple pronunciation guide is:

mee EE-rahs REK-teh ahl lah stah-tsee-DOH-moh

A few useful points:

• mi sounds like mee
• iras has stress on IR
• rekte has stress on REK
• stacidomo has stress on DO

Esperanto stress is very regular: it falls on the second-to-last syllable.

So:

• i-ras
• rek-te
• sta-ci-do-mo

Yes. Rekte is optional.

• Mi iras al la stacidomo = I am going to the train station
• Mi iras rekte al la stacidomo = I am going straight/directly to the train station

So rekte adds extra information, but the sentence is complete without it.