Osteoporosis and fragility fractures (FFs) are closely intertwined as the former is a common predisposing factor to the latter. This causal relationship is due to low bone density of osteoporosis and compromised bone microarchitecture, leading to structural failure, decreased ability to withstand applied stresses, and increased propensity to fracture. Osteoporosis can be idiopathic or due to a variety of secondary causes, and numerous treatment strategies are available. FFs are common injuries among the elderly and are caused by factors both intrinsic and extrinsic to the patient. The clinical and economic significances of osteoporosis and FFs are substantial, with considerable associated morbidity and mortality, and billions spent on healthcare expenditures in the US annually. Osteoporosis and FFs are two of the most important topics related to fracture liaison services (FLSs), and their understanding is integral to appreciating the benefits an FLS can provide for patients and providers.