Colloquial Expressions and Idioms

In informal speech and writing, es is commonly contracted with the preceding word by 's.  Geht es = geht's

Es is also used as an impersonal pronoun (es regnet, it's raining), but it can also be used as an introductory word for emphasis or stylistic reasons.  Es begins the sentence, and the true subject follows the verb.

Es ist niemand zu Hause.  No one is at home.
Es kommen heute drei Kinder.  Three children are coming today.

Es can also be used to anticipate a dependent clause or infinitive phrase.  This is almost like in English when we say I hate it when that happens instead of I hate when that happens.  "It" has no real meaning in the first sentence, but it is not incorrect to say it.

Ich kann es nicht glauben, daß er sich vor nichts fürchtet. I can't believe that he's not afraid of anything.
Er haßt es, nichts davon zu wissen.  He hates not knowing anything about it.

Other idioms:

Sie ist mit ihrem Urteil immer sehr schnell bei der Hand.  She makes her judgments rather quickly. (Literally: She is quick at hand with her judgments.)

Alles ist in Butter.  Everything is fine.  (Literally:  Everything is in butter.)

Er geht mit dem kopf durch die Wand.  He does as he pleases.  (Literally:  He goes with his head through the wall.)