This Perspective proposes definitions for key terms in the field of HIV-1 latency and eradication. In the context of eradication, a reservoir is a cell type that allows persistence of replication-competent HIV-1 on a timescale of years in patients on optimal antiretroviral therapy. Reservoirs act as a barrier to eradication in the patient population in which cure attempts will likely be made. Halting viral replication is essential to eradication, and definitions and criteria for assessing whether this goal has been achieved are proposed. The cell types that may serve as reservoirs for HIV-1 are discussed. Currently, only latently infected resting CD4(+) T cells fit the proposed definition of a reservoir, and more evidence is necessary to demonstrate that other cell types, including hematopoietic stem cells and macrophages, fit this definition. Further research is urgently required on potential reservoirs in the gut-associated lymphoid tissue and the central nervous system.