I have already written a couple of posts about 'tener', whish is the verb for 'to have' in the sense of possessing something. There is another word for 'to have' though - 'haber'.
Haber is used in forming compound tenses in the same way that 'have' is in English.
he hecho = I have done
ha comido = he/she has eaten
han llamado = they have called
Using different tenses of 'haber' allows more complicated expressions
había llegado = I/he/she had arrived
habiamos puesto = we had put
habría dicho = I/he/she would have said
habrán ido = they will have gone
Note that all the phrases above use the past participle of the second verb, both in Spanish and English.
Haber used alone means 'there is' or 'there are'.
hay mucho viento hoy = there is a lot of wind today
hay una buena tienda allí = there is a good shop there
¿hay pan? = is there (any) bread?
hay tres arboles = there are three trees
había una casa = there was a house
había cuatro gatos = there were four cats
habrá dos sillas = there will be two chairs
Finally for today, like 'tener', 'haber' can be used to say 'have to' or 'must'. In this case it is used with 'de' for a specific person and 'que' in an impersonal sense.
haber de = to have to
ha de = he/she has to, he/she must
hay que = one has to, one must (this is much more common than in English)