Animal rescue organizations are not animal shelters, but share the same goal as animal shelters in placing homeless pets with adoptive families. Animal shelters are characterized as having a physical location dedicated to housing and caring for many different types of animals, whereas most rescue groups work with one specific breed or type of animal and have volunteers who keep the animals in their homes until adoption, also known as foster care.

Rescue groups often obtain animals from local animal shelters, with the larger of these groups often transporting animals from locations that have a high number of homeless animals to locations where animals are more in demand. Rescue groups are often tied to national breed clubs for a given type of animal.