The verb “to have” serves two primary functions. First, it is used as a main verb to indicate possession. Second, it is used as a helper verb along with another verb to indicate various tenses.

• Main verb, possession: I have a car. It has four seats. Their car had four flat tires.
• Helper verb, present perfect: I have learned some useful information in this course. It has been interesting.
• Helper verb, past perfect: I had learned some information that had been useful to me.
• Helper verb, future perfect: I hope that I will have learned from the course, and that it will have been fun.

Note that the phrases “have to” and “have got to” are verbal phrases that mean approximately “must”.