A kártyapakli az asztalon van.

They mean the same thing: the. The choice depends on the sound that follows.

• a is used before a word beginning with a consonant: a kártyapakli
• az is used before a word beginning with a vowel: az asztalon

So the difference is about pronunciation, not meaning.

Because asztalon begins with a vowel sound, Hungarian uses az before it. This helps the phrase sound smoother.

So:

• az asztalon = correct
• a asztalon = incorrect

This is very similar to how English uses a and an.

Kártyapakli means deck of cards.

It is a compound noun:

• kártya = card
• pakli = pack, deck

Hungarian very often combines nouns into one word, so kártyapakli is literally something like card-deck.

Because Hungarian uses case endings instead of separate prepositions in many situations.

• asztal = table
• asztalon = on the table

The ending -on here expresses the idea of on.

So instead of saying a separate word for on, Hungarian adds a suffix to the noun.

In this sentence, -on means on in the sense of being on a surface.

So:

• asztal = table
• asztalon = on the table

This belongs to a group of location endings in Hungarian. With some nouns you get:

• -on
• -en
• -ön

Which one appears depends partly on the word itself and Hungarian sound patterns. For asztal, the correct form is asztalon.

Van means is.

In this sentence, it is needed because the sentence expresses location:

• A kártyapakli az asztalon van. = The deck of cards is on the table.

This is important because Hungarian often leaves out van in simple equational sentences in the present tense, such as:

• A kártyapakli új. = The deck of cards is new.

But with location, van is normally present:

• A kártyapakli az asztalon van.

That is the most neutral word order here. Hungarian word order is flexible, but it is not random: it reflects topic and emphasis.

In A kártyapakli az asztalon van:

• A kártyapakli is the topic: what we are talking about
• az asztalon van says where it is

Putting van at the end is very natural in a neutral statement of location.

A different order can change the emphasis. For example:

• Az asztalon van a kártyapakli. = The deck of cards is on the table.
  This can sound more like you are emphasizing the location.

Yes. That is also grammatical.

The difference is mainly in information structure:

• A kártyapakli az asztalon van.
  Topic: the deck of cards

• Az asztalon van a kártyapakli.
  Topic/emphasis: the table / the location

Both can translate the same way in English, but Hungarian uses word order to highlight what is already known and what is being presented as important.

Because Hungarian usually expresses ideas like in, on, under, to, from, and so on with suffixes attached to nouns.

So English says:

• on the table

But Hungarian says:

• asztalon

This is one of the biggest structural differences between English and Hungarian.

Usually, yes. In sentences like this, a and az are the definite article, equivalent to English the.

So:

• a kártyapakli = the deck of cards
• az asztalon = on the table

Hungarian uses the definite article very regularly, though article usage does not always match English perfectly in every context.

Because Hungarian does not need a subject pronoun here. The noun A kártyapakli already tells you what the subject is.

Hungarian often leaves out pronouns when they are not needed. So instead of something like It is on the table, Hungarian simply says A kártyapakli az asztalon van if the noun is stated.

It is one word: kártyapakli.

Hungarian commonly writes compound nouns as a single word. English often uses multiple words where Hungarian prefers a compound.

So:

• English: deck of cards
• Hungarian: kártyapakli

The accents mainly show vowel length.

• á is a long a
• a is a shorter, different vowel
• ó, é, í, ú, ő, ű also mark long vowels in Hungarian

In kártyapakli, the á matters. Hungarian spelling is quite regular, so accents are not optional decoration; they are part of the word.

Also, stress in Hungarian normally falls on the first syllable of the word:

• KÁR-tya-pak-li
• ASZ-ta-lon

Because Hungarian, like English, often uses the definite article when the object is specific and identifiable in the situation.

So az asztalon means on the table, not just on a table.

If you wanted on a table, you would use the indefinite article:

• egy asztalon = on a table

But in your sentence, the meaning is definite: a specific table is meant.