The Endangered Species Act creates two groups of protected species: endangered and threatened. The term "endangered" species refers to one that is in danger of extinction throughout all or a significant portion of its range. A "threatened" species is one that is likely to become endangered within the foreseeable future. Once a species is listed as endangered, it cannot be "taken" (harassed, harmed, pursued, hunted, shot, wounded, killed, trapped, captured, or collected).

Section 7 of the Endangered Species Act requires a determination of whether endangered or threatened species may be present in the area of a proposed activity. To ensure that any action authorized, funded or carried out by a federal agency is not likely to jeopardize the continued existence of any endangered or threatened species, consultation with, and assistance from the Secretary of the Interior and the Secretary of Commerce is required. Authority to conduct consultation under section 7(a)(2) of the Endangered Species Act has been delegated by the Secretary of the Interior to the Director of the Fish and Wildlife Service for terrestrial and freshwater aquatic species, and by the Secretary of Commerce to the National Marine Fisheries Service (NMFS), an agency within the National Oceanic and Atmospheric Administration, for anadromous and marine species.