Spieghi cosa significa questo dato e dica che ci importa.

Yes. They are formal commands addressed to Lei (the polite singular you).

In Italian, the formal imperative usually uses the present subjunctive form:

• spiegare → spieghi
• dire → dica

So:

• Spieghi ...
• Dica ...

mean Explain ... and Say ... when speaking politely to one person.

If you were speaking informally to one person, you would normally say something like:

• Spiega ...
• Di' ...

The h is there to keep the hard g sound.

In Italian:

• gi / ge usually sound like the j in jam
• ghi / ghe keep the hard g sound, like g in go

So:

• spieghi is pronounced with a hard g
• without the h, the spelling would not represent the correct sound

This happens in many verbs ending in -gare, such as:

• pagare → paghi
• spiegare → spieghi

Because cosa significa questo dato is an embedded question meaning what this piece of data means.

The command is only in spieghi:

• Spieghi = Explain

What follows is the content of the explanation:

• cosa significa questo dato = what this datum / data point means

So significa is not another command. It is the normal present indicative form of significare.

Here dato is a noun meaning datum, data point, piece of data, or sometimes figure/fact, depending on context.

A useful thing to remember:

• singular: dato
• plural: dati

So Italian commonly treats this as a normal countable noun:

• questo dato = this data point / this datum
• questi dati = these data

That is different from English, where data is often used as a mass noun.

Because questo already works as a determiner, like this in English.

So Italian says:

• questo dato = this data point

not:

• il questo dato

This is the normal pattern with demonstratives:

• questo libro = this book
• questa idea = this idea

Literally, ci importa means it matters to us.

Breakdown:

• importare = to matter
• ci = to us

So:

• ci importa = it matters to us
• more naturally in English, sometimes we care about it

Italian often uses importare the way English uses matter:

• Mi importa = It matters to me
• Ti importa = It matters to you
• Ci importa = It matters to us

The subject is the thing that matters.

In this sentence, the subject is understood from context — most likely questo dato or what that data represents.

So the logic is:

• questo dato ci importa = this data point matters to us

Italian often does not repeat the subject if it is already clear from the context.

This is a very good question, because this is the part of the sentence that may sound unusual to a learner.

As written, che most naturally means that:

• dica che ci importa = say that it matters to us

If the intended meaning is say why we care, standard Italian would more naturally be:

• dica perché ci importa
• or dica perché ce ne importa

So if you were shown the meaning say why we care, it is worth knowing that the Italian sentence as written is a bit odd for that meaning. Many native speakers would expect perché, not che.

Often, yes.

There is a small nuance:

• ci importa focuses on it matters to us
• ce ne importa often feels closer to we care about it

The ne points back to the thing being discussed.

So a very natural version for say why we care about it would be:

• dica perché ce ne importa

But ci importa is still understandable, especially if the idea is simply it matters to us.

Yes. Both are possible.

• cosa significa questo dato
• che cosa significa questo dato

Both mean what this data point means.

In everyday Italian, cosa by itself is very common and completely normal. It is a bit shorter and lighter, so it often appears in speech and writing.