Qu’est-ce que c’est ?

Because the sentence has two different jobs happening at once:

• qu’est-ce que is a question pattern meaning something like what is it that...
• c’est is the actual statement part, meaning it is / this is / that is

So:

• qu’est-ce que = the question frame
• c’est = the thing being asked about

That is why you see something that looks repetitive. It is normal French, not a mistake.

Very literally, it is something like what is it that.

Breakdown:

• que / qu’ = what
• est-ce que = a very common way to mark a question

So Qu’est-ce que c’est ? is built like:

• What is it that it is?

But that is only the literal structure. You should not translate it word for word in normal English. It is just the standard French way to ask this question.

Because French often drops the final vowel before a word starting with a vowel sound. This is called elision.

So:

• que est-ce que becomes qu’est-ce que
• ce est becomes c’est

French does this to make pronunciation smoother.

You would not normally write:

• Que est-ce que c’est
• Ce est

Those forms are incorrect in standard French.

In standard French, que is usually used before a verb, while quoi is usually used after a verb, after a preposition, or by itself.

So:

• Qu’est-ce que c’est ? = standard pattern with que
• C’est quoi ? = common informal pattern with quoi

Both are natural, but they are built differently.

A useful shortcut:

• que often appears in more structured question patterns
• quoi often appears in more informal or end-position questions

It is neutral and very common. You can use it in everyday speech and in writing.

It is neither especially formal nor especially slangy.

Compare:

• Qu’est-ce que c’est ? = neutral, standard
• C’est quoi ? = more informal, very common in speech

So if you are unsure, Qu’est-ce que c’est ? is a safe choice.

They usually mean the same thing, but the tone is a little different.

• Qu’est-ce que c’est ? = more standard / more textbook / neutral
• C’est quoi ? = more conversational / more informal

In real life, native speakers use both.

If you are learning French and want a reliable standard form, use Qu’est-ce que c’est ?
If you hear C’est quoi ? often, that is completely normal too.

It can depend on context.

In c’est, ce is often best understood as a general this / that / it kind of pronoun. French does not always separate these ideas the same way English does.

So Qu’est-ce que c’est ? may be understood as:

• What is this?
• What is that?
• What is it?

The exact English version depends on the situation.

For example:

• if you are holding an object, it may feel like What is this?
• if you are pointing at something farther away, it may feel like What is that?

French uses the same sentence in all these cases.

A common pronunciation is approximately:

kess kuh say

More carefully:

• Qu’est sounds roughly like kess
• ce que sounds like suh kuh or sometimes more reduced in fast speech
• c’est sounds like say

In natural speech, French speakers often run it together smoothly, so it may sound something like:

kess-ke-say

You do not need to pronounce every written letter strongly. French speech is often more connected than the spelling suggests.

Because est-ce is a fixed expression in French question formation.

In est-ce que, the est-ce part is written with hyphens:

• est-ce que

This is just the standard spelling. It is not optional.

So write:

• Qu’est-ce que c’est ?

not:

• Qu’est ce que c’est ?

Yes. It can be used very broadly.

You can use Qu’est-ce que c’est ? when:

• you see an unfamiliar object
• you hear a strange noise
• you notice something surprising
• you want to know what something is

For example, it can refer to:

• a thing
• a smell
• a sound
• an event

So it is not limited to physical objects.

Yes. French also has longer versions such as:

• Qu’est-ce que c’est que ça ?
• Qu’est-ce que c’est que ce bruit ?

This adds an extra element like ça or a noun phrase after the question.

It can sound a bit more explicit, emphatic, or expressive, depending on context.

Compare:

• Qu’est-ce que c’est ? = What is that / this / it?
• Qu’est-ce que c’est que ça ? = What is that? / What on earth is that?

The shorter form is extremely common, but the longer one is also natural.

Yes, very often.

Since the question asks what something is, a natural answer usually starts with C’est...

For example:

• Qu’est-ce que c’est ?
• C’est un livre.

or

• C’est une lampe.

This is one reason the sentence is useful for beginners: the question and the answer often use the same very common structure, c’est.