Dogs lick their owners as a way to show affection. This is especially common for puppies, who lick their mothers as a way to stay close to them.
Dogs also lick themselves as a way to groom themselves. This helps to keep their fur clean and free of dirt and debris.
Dogs also use licking to communicate with each other and with humans. For example, a dog may lick your hand to ask for food or attention.
Sometimes, dogs lick as a way to get attention. If you ignore your dog when they lick you, they may start licking more and more in an attempt to get your attention.
If you're eating something that smells good, your dog may lick you in an attempt to get a taste.
Licking can also be a way for dogs to relieve stress. If your dog is feeling anxious or stressed, they may lick you or other objects in an attempt to calm themselves down.
If you have a cut or open wound, it's important to avoid letting your dog lick it, as this could increase the risk of infection.