Haber as an Auxiliary Verb in Compound Tenses
When used as an auxiliary verb, haber is the equivalent of the English auxiliary "to have" (which is much different than the English "to have" when it means "to possess"). Haber is used to form what is known as the perfect tenses because they refer to actions that have been or will be completed. ("Completed" used to be a common meaning of "perfect.") As in English, the perfect tenses are formed by following a form of haber with a past participle.
He comprado un coche. (I have bought a car.)
Haber for 'There Is" or 'There Are'
Hay dos sillas en la cocina. (There are two chairs in the kitchen.)
Haber in Idioms
Haber can be used in a number of idioms, which are phrases that have a meaning apart from the meanings of the words in them. The one you'll run into most often as a beginner is haber que, which means "to be necessary" when followed by an infinitive. When used this way in the present tense, the hay form of haber is used.
Hay que conocerlo para comprenderlo. (It is necessary to know him in order to understand him.)
