This document defines orthodontic anchorage and provides a classification system. It discusses different types of anchorage according to the manner of force application, location in the jaws, and number of anchorage units. Intraoral anchorage options include teeth, alveolar bone, basal bone, and musculature. Extraoral options include cranial, cervical, and facial bones. Mini dental implants are also discussed as an anchorage option, including their classification and sites of placement. Factors to consider in anchorage planning and types of anchorage loss are outlined.