How to use "é que"?
I often see it in questions.Is it similar to French?
How would you translate it?

Question

How to use "é que"?
I often see it in questions.Is it similar to French? 
How would you translate it?

Answer

Well, without a context, it's hard to explain. It's not so common or a general rule. In addition to what Arthur explained, it would be like a contraction of "É porque" too. It's often used in informal situations. Lets look some examples.

- Why does the moon shine?
- It's because...

Translating (formal):
- Por que a lua brilha?
- É porque...

Translating (informal):
- Por que a lua brilha?
- É que...

Answer

Obrigado! 
I understood.I just wanted to know.However I think I won't use it a lot.

Answer

Actually "é que" is not an expression.
You don't have to use verb "ser" (é, foi) with some interrogatives ("Como", "Quem"...)
But...
If you decide to use it, and after verb SER comes another VERBAL sentence (I mean, a sentence with another verb in it), then conjunction "que" must be used to introduce the following verbal sentence.

Examples: 
Como  - te chamas? (not using verb "ser")
Como é - teu nome? (using verb "ser", but no verbal sentence comes after)
Como é - QUE te CHAMAS? (using verb "ser", with a verbal sentence after - verb "CHAMAR")

Another example with verb SER in past tense (FOI in place of É)
Quem - te deu esse livro? (without verb "SER")
Quem foi - teu professor? (with verb "SER", no verbal sentence after)
Quem foi - QUE te DEU esse livro?

Quem dirige o espetáculo? 
Quem é o diretor do espetáculo? 
Quem é QUE DIRIGE o espetáculo?

O que você quer?
O que é um Banco de Dados?
O que é QUE você QUER?

Answer

Sorry for this! Maybe this question will show what I mean :Como é que te chamas?
It's a very easy one.What's the sense of this construction if the meaning is the same without it?

Answer

I am not sure but i think it means, and that.