Who is Queen Katherine of Aragon from The Other Boleyn Girl and what is their importance?

Queen Katherine of Aragon was Henry VIII's first wife. Their daughter Mary later became the Queen of England. Henry divorced Katherine after falling in love with Anne Boleyn, claiming their marriage wasn't a true marriage because his brother had been wed to Katherine before him. Mary Boleyn loved Queen Katherine, even after bearing the king two children of her own.