A dog communicates with people and other animals using a variety of physical gestures. Usually when a dog is feeling friendly and happy, it wags its tail; sometimes you can almost see a smile on the dog's lips. Conversely, when a dog is showing remorse, it may put its tail between its legs and lower its head as it approaches its owner. When a dog is angry or protecting its property, it will raise the hair on its back and bare its teeth as a physical sign of aggression. A dog will roll over onto its back and show its throat to its aggressor as a sign of submission. A dog that wants your attention will rub against your legs while looking at you expectantly, hoping for some petting or a walk. Many house-trained dogs sit by the door or scratch at the door when they need to go outside. Dogs communicate with other dogs by smells, such as urinating to mark their territory and sniffing. A dog may nip at another dog or small child to correct its behavior.
Dogs use quite a lot of vocal communication with humans as well as other animals. They may bark and whine as a sign of welcome when you arrive home. They also use a more aggressive bark with growls to tell a stranger to stay away. A house-trained dog may whine by the door to be let outside. A hungry dog may whine by its empty food dish to remind you to feed it. Some dogs enjoy singing using a variety of pitches in their howls. A dog in pain may whine repeatedly, lie down or stay close to its owner. A dog seeking its owner's praise and approval will respond quickly to its owner's commands and then seek attention.
A dog that wants to play catch may bring you a ball, set it at your feet and bark at you. Some dogs leave their "kill" near the doorstep. They want you to know that they are protecting you and providing for you. They want your praise for their job as well. A bored dog may chew up your favorite quilt or destroy furniture to tell you that it needs more stimulation or exercise.