Això és important de debò.

Això is a demonstrative pronoun, so it stands on its own and means this or this thing / this matter.

Aquest is usually a demonstrative adjective, so it normally goes before a noun: aquest llibre = this book.

So:

• Això és important = This is important
• Aquest llibre és important = This book is important

In your sentence, there is no noun after això, so això is the natural choice.

It usually refers to a situation, idea, fact, or thing that is being pointed out in the conversation. It is often a bit broader than English this, and can mean something like this matter, this, or what we’re talking about.

For example, if someone has just explained a problem, Això és important means That/This is important in the sense of what you just mentioned is important.

És is the 3rd person singular of ser, meaning is.

The accent is important because it distinguishes és from es:

• és = is
• es = a reflexive/clitic pronoun, like himself / herself / itself / each other, depending on context

So in this sentence, és must have the accent because it is the verb is.

A rough pronunciation guide is:

• això ≈ eye-SHAW or ah-SHAW, depending on accent
• és ≈ ess
• important ≈ eem-por-TANT
• de debò ≈ duh deh-BOH

A more natural overall rhythm is something like:

ah-SHAW ess eem-por-TANT duh deh-BOH

A few useful pronunciation notes:

• In això, the x sounds like sh
• The final ò in això and debò is stressed and open
• In connected speech, de debò flows together quite smoothly

De debò means really, for real, or seriously.

So Això és important de debò means something like:

• This is really important
• This is genuinely important
• This is seriously important

It adds emphasis. The speaker is not just saying it is important, but stressing that it is truly important.

They are similar, but not always identical in tone.

• de debò often sounds a bit more idiomatic, conversational, and emphatic
• realment is more directly like really or actually, and can sound slightly more neutral or formal depending on context

So:

• Això és important de debò = This is really / genuinely important
• Això és realment important = This is really important

Both work, but de debò often gives a stronger feeling of for real / genuinely.

They are very close. In many contexts, both mean really or truly.

• de debò = for real / really / genuinely
• de veritat = really / truly

In everyday speech, they are often interchangeable. The difference is mostly one of style and habit rather than basic meaning.

So all of these are possible:

• Això és important de debò
• Això és important de veritat
• Això és realment important

Because this is a normal ser + adjective structure in Catalan, just as in English:

• Això és important
• This is important

The adjective comes after the verb when it describes the subject. That is completely standard.

Yes, predicate adjectives agree in Catalan, but here you do not see much change because important has the same form for masculine and feminine singular.

With això, Catalan generally uses a neuter idea, and adjectives commonly appear in the singular, often in the masculine singular if there is a visible distinction.

For example:

• Això és important
• Això és bo
• Això és estrany

If the subject were plural, the adjective would change:

• Aquestes coses són importants = These things are important

Yes, but the sentence as given is very natural.

The most straightforward version is:

• Això és important de debò

You may also hear emphasis expressed differently, for example:

• Això és de debò important in some speech, though this is less neutral
• Això és realment important
• De debò, això és important if de debò comments on the whole statement

For a learner, Això és important de debò is the safest and most idiomatic pattern to remember.

Yes. De debò? is a very common expression meaning Really? or For real?

So the phrase is useful both:

• inside a sentence: Això és important de debò
• by itself: De debò?

Yes, if the context already makes clear what you are talking about.

• Això és important de debò = explicitly says this
• És important de debò = It’s really important, with the subject understood from context

Catalan often leaves out subjects when they are clear, but here això is included because the speaker wants to point to a specific thing, idea, or situation.

Yes. It sounds natural and idiomatic.

It is a good everyday way to strongly emphasize importance. It feels a bit stronger than just Això és important because de debò adds the sense of genuinely, seriously, or for real.