A priest is a person whose job is to perform religious rites and ceremonies.
A principal is someone who runs a school, doing more administrative work than teaching. In some countries, a principal is called a headmaster or headmistress.
A prison, also called a jail, gaol or penitentiary, is a place where people who have done bad things are locked up as a punishment. Some people can be put in jail for many, many years because they have done something very, very bad.
A prisoner, also called an inmate, is someone who has done something bad and been put into prison as a punishment.
A prize is something you get given when you win a competition. A prize may be a special ribbon like in the picture, a trophy, or some money.