Who is The Dursleys (Dudley, Vernon, and Petunia) from Harry Potter and the Order of the Phoenix and what is their importance?

The Dursleys are Harry Potter's relatives. His Aunt Petunia is his mother’s sister. The Dursleys are described as mean people, but the power of Aunt Petunia's blood protects Harry. The Dursley's raised Harry until he started school at Hogwarts when he was eleven-years-old.