Shepherd is a type label rather than a single breed. On adoption listings it most often points to a German Shepherd or a German Shepherd mix, though Australian, Belgian, Dutch and English Shepherds and their crosses fall under it too. What they share is ancestry in herding and flock-guarding work, which gave them stamina, sharp minds and a habit of staying close to their people.
Most are medium to large, with a thick shedding coat. Many are loyal and quick to learn, and some are reserved or protective with strangers, so early socialization and steady training pay off. Herding instincts can show up as nipping or chasing bikes, cats and kids. Ancestry varies widely, so a dog's own history and behavior tell you more than the label does.