koya ni nimotu wo oita.

A natural reading is:

こや に にもつ を おいた。

• 小屋 = こや
• 荷物 = にもつ
• 置いた = おいた

So the full sentence is:

こや に にもつ を おいた。

小屋 usually means a hut, shed, or small cabin-like structure.

In this sentence, the exact English word depends on context:

• a shed
• a hut
• a small cabin

So 小屋に荷物を置いた could mean something like:

• (I) put the luggage in the shed
• (I) left the सामान in the hut

Here, に marks the place where something is put.

With the verb 置く (to put / place / leave), the location where the object ends up is often marked with に.

So:

• 小屋に = in/at the shed
• 荷物を = the luggage
• 置いた = put / placed / left

This is different from で, which often marks the place where an action happens in a broader sense. With 置く, に is the normal choice because it marks the destination/location of placement.

を marks the direct object of the verb.

The thing being put down is 荷物 (luggage / baggage / belongings), so it takes を.

• 荷物を置いた = put the luggage
• 何を置いた？ = What did (someone) put down?
• 荷物を = the luggage as the thing affected by the action

The dictionary form is 置く (おく).

This verb means:

• to put
• to place
• to set down
• sometimes to leave

置いた is the past tense form, so it means:

• put
• placed
• left

Formation:

• 置く → 置いた

This is a standard past-tense pattern for verbs ending in -く.

It can mean either, depending on context.

Common possibilities:

• put down / placed
• left

So 小屋に荷物を置いた could mean:

• I put the luggage in the shed
• I left the luggage in the shed

Japanese often leaves this kind of nuance to context. If the broader situation is about physically placing something somewhere, put is natural. If the emphasis is that the luggage remained there, left may sound better in English.

The subject is omitted.

This is extremely common in Japanese. If the meaning is already clear from context, Japanese often does not say I, he, she, or they.

So this sentence could mean:

• I put the luggage in the shed
• He put the luggage in the shed
• She left the luggage in the shed
• etc.

You figure out the subject from context, not from the sentence alone.

Yes, Japanese word order is fairly flexible as long as the particles stay attached to the right words.

This sentence is most neutral as:

小屋に荷物を置いた。

But you may also see:

• 荷物を小屋に置いた。

This means the same thing. The difference is mostly one of emphasis or flow, not basic meaning.

What matters most is:

• 小屋に stays together
• 荷物を stays together

Because this sentence is just giving a simple action: put the luggage in the shed.

You use は when you want to mark the topic, for example:

• 私は小屋に荷物を置いた。
  As for me, I put the luggage in the shed.

But if the subject or topic is already understood, Japanese often leaves it out completely. That makes the shorter version very natural:

• 小屋に荷物を置いた。

荷物 does not clearly mark singular vs. plural by itself.

It can mean:

• a piece of luggage
• luggage
• baggage
• belongings

Japanese nouns usually do not change form for singular and plural the way English nouns often do.

So 荷物を置いた could mean:

• put the luggage
• put the bags
• left the belongings

The exact number depends on context.

Usually に is the better and more natural choice with 置く.

That is because に marks the place where the object is placed. へ mainly emphasizes direction toward somewhere, and it is more common with motion verbs like:

• 行く = go
• 来る = come
• 帰る = return

Since 置く is about placing something at a location, に fits much better:

• 小屋に荷物を置いた。 = natural

It is plain style and neutral-casual:

• 置いた = plain past

A more polite version would be:

• 小屋に荷物を置きました。

So:

• 置いた = casual/plain
• 置きました = polite

The plain form is very common in everyday speech, narration, and informal writing.