La baraja está sobre la mesa.

Because this sentence is talking about location: where the deck is. In Spanish, location is normally expressed with estar, not ser.

• La baraja está sobre la mesa. = The deck is on the table.
• Es would sound wrong here for location.

A very common rule learners hear is: ser is for identity/essential characteristics, and estar is for states and location.

The accent mark shows which syllable is stressed: es-TÁ.

It also helps distinguish this form from esta, which can mean this:

• esta mesa = this table
• está sobre la mesa = is on the table

So the written accent is important both for pronunciation and meaning.

Baraja usually means a deck of cards in this kind of sentence.

In different contexts, it can also relate to playing cards more generally. For a learner, the safest understanding here is:

• la baraja = the deck of cards

Depending on region and context, people might also say mazo (de cartas) for deck, but baraja is a very normal word.

In Spanish, every noun has a grammatical gender, usually masculine or feminine. Here:

• baraja is feminine, so it takes la
• mesa is feminine, so it also takes la

That is why you get:

• la baraja
• la mesa

This is grammatical gender, not biological gender. Objects are simply assigned a gender in Spanish and articles must match.

Here, sobre means on, on top of, or over.

So:

• sobre la mesa = on the table

It is a preposition. In everyday Spanish, encima de can sometimes express a similar idea:

• La baraja está encima de la mesa.

But sobre is perfectly correct and common.

Sometimes, but the meaning is a little different.

• sobre la mesa clearly means on top of the table
• en la mesa can sometimes mean on the table, but depending on context it may feel less precise or more like at the table / on the surface of the table

If you want to emphasize physical position on the surface, sobre is a very clear choice.

Yes, Spanish word order is flexible, but this is the most neutral and natural order:

• subject + verb + prepositional phrase

So:

• La baraja = subject
• está = verb
• sobre la mesa = location

You might also hear:

• Sobre la mesa está la baraja.

That version is grammatical, but it sounds more marked or emphatic, as if highlighting where it is.

In normal Spanish, you need the articles here.

• La baraja está sobre la mesa. = natural
• Baraja está sobre mesa. = not natural / incorrect in standard usage

Spanish uses articles more often than English does. Even when English might sometimes omit the, Spanish often keeps it.

A simple approximation is:

lah bah-RAH-hah es-TAH SOH-breh lah MEH-sah

A few key points:

• j in baraja sounds like a strong English h sound
• r in baraja is a light tap
• está is stressed on the last syllable
• mesa is stressed on me

A more Spanish-like pronunciation would be smoother and shorter in the vowels than in English.

Yes, baraja is singular:

• la baraja = the deck

The plural is:

• las barajas

So:

• Las barajas están sobre la mesa. = The decks are on the table.

Notice that both the article and the verb change:

• la baraja está
• las barajas están

Because Spanish verbs must agree with the subject in number.

• La baraja está = singular subject
• Las barajas están = plural subject

This is very common in Spanish. The verb changes depending on who or what is doing the action or being described.

In most normal contexts, sobre la mesa will be understood as on the table.

Although sobre can sometimes have a broader sense like over or above, this sentence most naturally suggests that the deck is resting on the table, not floating above it.

If you really wanted to say above the table, Spanish would usually make that clearer in another way.

Yes, this is correct and understandable across Latin America.

That said, in everyday speech, some speakers might prefer slightly different wording, such as:

• La baraja está en la mesa.
• La baraja está encima de la mesa.

Also, in some places, people may be more likely to say el mazo for the deck. But La baraja está sobre la mesa is perfectly good Spanish.