Hay... and More
The verb haber lives a double life. On the one hand, it can be a helping verb (also known as an auxiliary verb) that is used in all persons and numbers, tenses and moods to form the perfect tenses. On the other, it exists only in the third-person singular -- in all tenses and moods, as an impersonal verb, also often referred to as an existential verb.
In the present tense, this form is not the same as the form it uses when the third person singular is used to form the present perfect, e.g. Él ha comido. Instead, it is hay, meaning both there is and there are. Some learners, even at the intermediate level, still confuse the use of this verb with the functions of ser and estar. The difference can be shown easily with a couple of examples. If one wishes to say John is a man, the statement is personal and hay cannot be used, i.e., Juan es hombre. Likewise, if we want to say that John is here, we say Juan está aquí. These are personal statements, not impersonal ones. But if we see a man on the corner, we can say Hay un hombre en la esquina; if there are two or more men, we can say Hay muchos hombres en la esquina. These types of statements do not treat the man or men in a personal way.