The pouch is a distinguishing feature of female marsupial

Marsupial

Marsupials are an infraclass of mammals, characterized by giving birth to relatively undeveloped young. Close to 70% of the 334 extant species occur in Australia, New Guinea, and nearby islands, with the remaining 100 found in the Americas, primarily in South America, but with thirteen in Central...

s (and rarely in the males as in the water opossum

Water Opossum

The water opossum , also locally known as the yapok, is a marsupial of the family Didelphidae. It is the only member of its genus, Chironectes...

 and the extinct Thylacine

Thylacine

The thylacine or ,also ;binomial name: Thylacinus cynocephalus, Greek for "dog-headed pouched one") was the largest known carnivorous marsupial of modern times. It is commonly known as the Tasmanian tiger or the Tasmanian wolf...

); the name marsupial is derived from the Latin marsupium

Marsupium

Marsupium is the Latin word for a pouch in several animal groups:* Pouch , in marsupials* Brood pouch , in peracarid crustaceans* Brood pouch , in syngnathids such as sea horses...

, meaning "pouch

Pouch

Pouch may refer to:* A small bag such as a pocket, teabag, money pouch, sporran, etc* Cadaver pouch, body bag * Diplomatic pouch* Electric heating pouch, medical apparatus, electric heating device for curative treatment...

". Marsupials give birth to a live but relatively undeveloped fetus

Fetus

A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...

 called a joey. When the joey is born it crawls from inside the mother to the pouch. The pouch is a fold of skin with a single opening that covers the nipple

Nipple

In its most general form, a nipple is a structure from which a fluid emanates. More specifically, it is the projection on the breasts or udder of a mammal by which breast milk is delivered to a mother's young. In this sense, it is often called a teat, especially when referring to non-humans, and...

s to protect the joey as it continues to develop.

Pouches are different amongst the different marsupials: for example for Quoll

Quoll

The quoll, or native cat, is a carnivorous marsupial native to mainland Australia, New Guinea and Tasmania. It is primarily nocturnal and spends most of the day in its den. There are six species of quoll; four are found in Australia and two in New Guinea...

s and Tasmanian Devil

Tasmanian Devil

The Tasmanian devil is a carnivorous marsupial of the family Dasyuridae, now found in the wild only on the Australian island state of Tasmania. The size of a small dog, it became the largest carnivorous marsupial in the world following the extinction of the thylacine in 1936...

s, the pouch opens to the rear and the joey only has to travel a short distance to get to the opening (resting place) of the pouch.