One point vs process. Meditation is a state of relaxed focus concentration, most commonly on a single focus, be it breath, mantra, counting, a light, a body part, etc. An image can be the focus of attention. Guided imagery is a more active, often process or problem-solving focus on the unconscious process as displayed via imagery.
Breath vsImagination. Meditation: a mental technique, focused on breathing, repetitively practiced for the purpose of attaining a subjective experience that is frequently described as very restful, silent, & of heightened alertness, often characterized as blissful. Guided imagery: more active & proactive, though gentle but powerful technique that focuses and directs the imagination.