Biopsy is the removal and examination of tissue to diagnose a condition. It can be excisional, removing the entire lesion, or incisional, removing part of a lesion. Indications include persistent lesions without a clear cause, suspected tumors or malignancies, and lesions interfering with function. Contraindications are poor health and acute infection. Types include punch, frozen section, aspiration, and exfoliative cytology. Care must be taken in design, handling, and potential dangers like spreading or infection. Biopsy provides diagnostic and treatment guidance.