Lydia Hall developed a nursing theory in the late 1960s that defined nursing care as consisting of three interlocking levels: care, core, and cure. Care involves nurturing and comforting the patient through activities like teaching. Core focuses on developing a relationship with the patient using therapeutic communication to help them express feelings and develop maturity. Cure involves helping patients through medical treatments prescribed by doctors, taking on a more negative role of avoiding pain. The theory emphasizes providing total care to individuals from birth to end of life that considers all three aspects.