Question

para que sirve y como se utiliza y 2 ejemplos de cada una:
frist conditional

second conditional

third conditional

Answer 1

First conditional (type 1): Sirve para hablar de una situación que es real o posible  y se utiliza de la siguiente manera:

if+ simple present (presente simple)+ simple future (futuro simple)

Por ejemplo, 

If he doesn't do his homework, he can not go out tonight.

If it rains, we can't go to the beach.

If you spend more than you earn, you'll become a poor man.

Second conditional (type 2): Sirve para referirse a una situación hipotética y se utiliza de la siguiente manera:

If+ Simple past (pasado simple)+ Simple conditional (condicional simple)

Por ejemplo,

If she wrote a book, it would be a best-seller.

If I had more money, I would buy a nice car.

If I were you, I wouldn't do that.

Third conditional (type 3): Sirve para hablar acerca de una situación hipotética del pasado y se utiliza de la siguiente manera:

If + Past perfect (pasado perfecto) + Conditional perfect (condicional perfecto)

Por ejemplo,

If you had phoned me, I would have known you were here.

If we had studied harder, we might have passed the test.

If she had explained me the problem, I would have understood it.