Originally bred in Germany from a cross between English bulldogs and the Belgian-German Brabanter Bullenbeisser breed, boxers are medium-sized, powerfully built dogs with strong, square jaws and short coats. Though they may appear intimidating, they have playful personalities and are good family dogs as they can withstand energetic children. There are several kinds of boxers, some based on coat color and others the product of cross-breeding.
When the German Boxer Klub initially set the breed standards, they only included white boxers, as these were the main kind when the dogs were introduced. Later on the brindle boxers became popular and widely accepted as pets and working dogs and the white boxers became rarer. Brindle dogs with a lot of white coloring on their bellies, feet, legs, and sides became known as "white" boxers, though they still had more color than the original white boxers did.
Brindle boxers were not allowed to participate in dog shows or contests when the breed first came into prominence, so instead were used as working and hunting dogs. When German police began using boxers for police work, they preferred the darker colored dogs to the white ones because they were not so obvious. In 1930 the German Boxer Klub began allowing brindle boxers to participate in events along with the white boxers.
Though some miniature boxers are bred from a succession of smaller and smaller parents, most are created through cross-breeding pugs and toy fox terriers, so they aren't truly boxers at all. But they do have very similar features and coloring to the actual boxer breed. They are on average 1/4 the size of a typical boxer.
Another product of cross-breeding, the bulldog boxer is a mix of boxer and a bulldog breed. In appearance they are often very similar to regular boxers, though size and facial features may vary depending on the exact breed they are crossed with. They also have some personality differences, picking up different characteristics from their nonboxer lineage.