The chapter provides a multidimensional analysis of hallucinations, emphasizing their phenomenological diversity, etiological complexity, and behavioral implications. Hallucinations are categorized by sensory modality—auditory, visual, tactile, olfactory, and gustatory—and further differentiated by content, emotional valence, and degree of conviction. The text explores neurobiological, psychological, and environmental origins, including dopaminergic dysregulation, trauma, sleep disruption, and substance use. It highlights the role of cognitive biases and stress-reactivity in the emergence and maintenance of hallucinatory experiences. Behavioral strategies are examined through a functional analytic lens, identifying avoidance, safety behaviors, and social withdrawal as common responses that may inadvertently reinforce hallucinatory distress. The chapter advocates for individualized assessment of hallucination function and context, promoting interventions that target maladaptive contingencies while enhancing coping and engagement. This integrative framework supports both clinical formulation and research development, bridging neuroscience, psychiatry, and behavior analysis to inform evidence-based practice.