Az eszköz a dobozban van.

A and az are the same definite article, meaning the. Hungarian uses:

• az before a vowel sound
• a before a consonant sound

So you say az eszköz because eszköz begins with a vowel, and a dobozban because dobozban begins with a consonant.

Because there are two separate noun phrases:

• az eszköz = the device/tool
• a dobozban = in the box

Hungarian often uses articles much like English does, so it is normal to have two definite articles in a sentence like this.

-ban is a case ending meaning in or inside.

So:

• doboz = box
• dobozban = in the box

This case is called the inessive case.

Hungarian usually expresses ideas like in, on, to, from, etc. with endings attached directly to the noun.

So instead of using a separate word like English in, Hungarian adds a suffix:

• doboz = box
• dobozban = in the box

This is a very common feature of Hungarian grammar.

Because of vowel harmony. Hungarian suffixes often change depending on the vowels in the word.

A very basic rule is:

• words with mostly back vowels take -ban
• words with mostly front vowels take -ben

doboz has back vowels (o, o), so it becomes dobozban.

Compare:

• dobozban = in the box
• székben = in the chair

That is a very common question. In Hungarian, the present-tense forms of to be are often omitted in the third person when the sentence links a subject to a noun or adjective:

• Az eszköz új. = The device is new.
• Az eszköz hasznos. = The device is useful.

But when you say where something is or that something exists, Hungarian normally uses van:

• Az eszköz a dobozban van. = The device is in the box.

So here van is needed because the sentence expresses location.

No, Hungarian word order is fairly flexible. The version you have, Az eszköz a dobozban van, is a neutral, natural sentence.

But other orders are possible if you want to change the emphasis. For example:

• A dobozban van az eszköz. puts more focus on where it is.
• Az eszköz van a dobozban. can sound contrastive, as if saying it is the device that is in the box.

So word order in Hungarian often reflects focus and emphasis, not just grammar.

The subject is Az eszköz.

That is the thing being talked about: the device/tool.
The rest tells you where it is:

• a dobozban = location
• van = is

So the structure is roughly:

• Az eszköz = subject
• a dobozban = location
• van = verb

dobozban is in the inessive case, which answers where? and means in.

Related forms are:

• dobozban = in the box
• dobozba = into the box
• dobozból = out of the box

These three often get learned together because they describe location, movement into, and movement out of something.

A few useful pronunciation points:

• sz is pronounced like English s in see
• Hungarian s by itself is pronounced like English sh
• ö has no exact English equivalent; it is similar to German ö or French eu

So eszköz begins with an s sound, not a sh sound.

If you want to say The devices are in the box, you would say:

Az eszközök a dobozban vannak.

Changes:

• eszköz → eszközök = plural noun
• van → vannak = plural are

So singular and plural are:

• Az eszköz a dobozban van. = The device is in the box.
• Az eszközök a dobozban vannak. = The devices are in the box.