Breed specific rescues are typically rescues that are run by show people or those involved with breeding quality show dogs. They work with a breed exclusively and help them in any way they can. These groups can be wonderful resources since they are very familiar with the qualities and characteristics of a specific breed.
There are also rescue organizations that specialize in mixed breed dogs such as poodle or lab mixes. If you have allergies, or are looking for a dog that sheds very little, consider a rescue that caters to that kind of designer dog rather than purchasing one. This way you’ll be getting the qualities you’re looking for without the heavy price tag and the potential issues later on.