The groups of population that can interbreed and are capable to give birth to their young ones only with members of their respective species having common characteristics are called Species.
The species of plants and animals that can be found only in a specific region are called Endemic species. They may be endemic to a zone, state or country. For example, Greater One-Horned Rhinoceros, Nilgiri Tahr, Bengal Tigers, Lion Tailed Macaque, etc. are some of the endemic animals of India.
The species of plants and animals whose number is reducing to a level where they may no more exist in nature are called Endangered species. For example, Bengal Tiger, Snow Leopard, Blackbuck, Indian Bison (Gaur), etc. are some of the fauna of India whose number has diminished to a level after which they may get exinct.
The species of plants and animals that no more exist in nature due to unsuitable habitat are called Extinct species. For example, Indian Aurochs, Sivatherium, Sumatran Rhinoceros, Pink-Headed Duck, etc. are some of the extinct animals of India.