Hestia is the goddess of the house, and of the hearth (fireplace) within the house, so she is the goddess of safety, security, doing your duty, taking care of things. Probably even though she is not in very many stories, she was actually a pretty important goddess, who was worshipped at home, as part of the ritual of lighting a fire or moving into a new house, or getting married.
To find out more about Hestia, check out these books from Amazon or from your library:
D'aulaire's Book of Greek Myths, by Edgar and Ingri D'Aulaire.
Greek Religion, by Walter Burkert (reprinted 1987). By a leading expert, for adults. He has sections on each of the Greek gods, and discusses their deeper meanings, and their function in Greek society.