The word kangaroo derived from the Australian Aboriginal word "gangurru" referring to the Grey Kangaroo. The name was first recorded as kangaru by botanist Joseph Banks on James Cook's first voyage in 1768–1771.

The belief that kangaroo means "I don't understand" (or "I don't know") is a popular myth that is also applied to some other Aboriginal-sounding Australian words.

Kangaroos feed on shrubs, grasses, leaves and herbs and usually graze in groups called mobs in the cool of the night, mornings and evenings. The life expectancy of a kangaroo is about 18 years.

Eastern grey kangaroos can leap up to nine meters in a single bound and hop as fast as 20–25 km per hour (13–16 mph). Kangaroos are also apt swimmers.

Gestation lasts between 30 and 38 days. At this stage, only the forelimbs are somewhat developed, to allow the peanut-sized joey (baby kangaroo) to climb to the pouch and attach to a teat where it will stay for 300 days. It is usually fed by its mother until the age of 18 months.

A female kangaroo has the ability to freeze the development of an embryo until the previous joey is able to leave the pouch, and change the composition of milk according to the needs of the joey. She is also able to simultaneously produce two different kinds of milk for the newborn and the older joey who still lives in the pouch.