La dormosako restas en la tendo.

Because Esperanto uses word endings to show the part of speech very clearly:

• -o = noun
  
  • dormosako = sleeping bag
  • tendo = tent
• -as = present tense verb
  
  • restas = remains / stays

This is one of the most helpful features of Esperanto: the endings tell you what kind of word you are looking at.

Yes, it is one compound word.

It is made from:

• dormo = sleep
• sako = bag

So dormosako is literally something like sleep-bag, which English expresses as sleeping bag.

Compounds are very common in Esperanto. Usually, the main idea comes at the end, so dormosako is a kind of sako.

La is the definite article, meaning the.

So:

• la dormosako = the sleeping bag
• la tendo = the tent

Esperanto has only one definite article: la. It does not change for gender, number, or case in normal use.

Also, Esperanto has no indefinite article. So English a tent is usually just tendo, not a separate word for a.

Restas comes from resti, which means to remain, to stay, or to be left.

So in this sentence, restas suggests that the sleeping bag is still in the tent or remains there, rather than simply existing there.

That can give a slightly different feeling from a plain statement of location.

Both can work, but they are not identical.

• La dormosako estas en la tendo. = The sleeping bag is in the tent.
  
  • This is a neutral statement of location.
• La dormosako restas en la tendo. = The sleeping bag remains/stays in the tent.
  
  • This emphasizes that it is still there or has not been moved.

So restas adds a sense of continuation.

Because this sentence describes location, not movement toward a place.

• en la tendo = in the tent
• en la tendon = into the tent

In Esperanto, the -n ending is often used not only for direct objects, but also to show direction toward something.

So:

• La dormosako restas en la tendo. = The sleeping bag stays in the tent.
• Mi metas la dormosakon en la tendon. = I put the sleeping bag into the tent.

Yes. Esperanto word order is fairly flexible, because the grammar is shown by endings and prepositions.

The basic order here is:

• La dormosako restas en la tendo.

But you could also say:

• En la tendo restas la dormosako.

That might sound more like In the tent remains the sleeping bag or It is in the tent that the sleeping bag remains.

The original version is the most neutral and straightforward.

A simple English-friendly approximation is:

lah dor-MO-sa-ko RES-tahs en lah TEN-do

A few helpful points:

• Stress in Esperanto is usually on the second-to-last syllable.
  • dormosako → dor-mo-SA-ko
  • restas → RES-tas
  • tendo → TEN-do
• Each vowel is pronounced clearly.
• Esperanto spelling is very regular, so pronunciation is much more predictable than in English.

To make nouns plural, add -j.

So:

• dormosako → dormosakoj = sleeping bags
• tendo → tendoj = tents

Examples:

• La dormosakoj restas en la tendo. = The sleeping bags remain in the tent.
• La dormosako restas en la tendoj. = The sleeping bag remains in the tents.

If both are plural:

• La dormosakoj restas en la tendoj.

Often, yes—or at least it suggests contrast with some other possibility.

Using restas can imply ideas like:

• it is still there
• it has not been taken away
• it stays behind
• it continues to be located there

So compared with estas, restas often carries a small extra nuance of persistence or non-movement.