Shepherd is a label for a type of dog, not a single breed. On adoption listings it most often means a German Shepherd or a German Shepherd mix, but Australian Shepherds, Belgian and Dutch Shepherds, English Shepherds and crosses with Labs or Huskies fall under it too. What they share is ancestry in herding and flock-guarding work.
Most are medium to large, athletic and smart, with a thick shedding coat and a strong wish to stay near their people. Many are loyal and quick to learn, and some are reserved or protective with strangers. They generally need daily exercise, training and a job to focus on. Because ancestry varies, size, energy and coat can differ a lot from one dog to the next, so judge the dog in front of you rather than the label.