Paget's disease progresses through three phases: an osteolytic or "hot" phase where bone is broken down irregularly, seen as a blade of grass or flame sign on x-ray; a mixed phase where new bone formation occurs in a jigsaw pattern but is improperly laid down, seen as a cotton wool skull or picture frame vertebrae; and a sclerotic or "cool" phase where bone is dense but weak, seen as a tam o'shanter skull shape on x-ray. The document provides an overview of the three phases and common radiographic findings of Paget's disease.