Dog breeds are typically divided into a few basic categories: companion dogs, guard dogs, hunting dogs, herding dogs and working dogs. The top dog breeds for every purpose are represented here. Despite the names, in contemporary America, most breeds - even hunting or herding dogs - service as companies for individuals and families.
Dogs have been selectively bred for thousands of years, sometimes by inbreeding dogs from the same ancestral lines, sometimes by mixing dogs from very different lines. The process continues today, resulting in a widening in appearance without speciation, "from the Chihuahua to the Great Dane."
Dogs with short coats also have another advantage. It is easier to find ticks and fleas on their body. You probably spend eight times as long searching for fleas and ticks on a dog with a long coat than you do on a dog with a short coat.
So keep in mind that if you choose a breed with a long coat you will either need to get it clipped regularly if you want to avoid brushing it so much, or if you choose to keep it long or even medium length you will have to brush it every day.