A cat has his own welcoming miaow which he will use only for his owner. Other people, even companion cats, will hear a different meow as their greeting. The cat will then rub against the owner's legs and may accompany this with a chirruping noise of greeting. He may bounce on stiff front legs, back slightly arched, with ears pricked up and tail held high.
Cats rub like this because they have scent glands around their chins and lips (and also anus), and when they rub they transfer this scent onto whatever they have touched, making the object or person smell more familiar. An owner who has been outside for a time will have lost some of his cat's scent, so the cat renews it.
When greeting a returned owner, the cat may be in such a hurry to say 'hi' that he does not use any of his scent glands, but simply rubs his side along the owner's legs. By bouncing, the cat can reach higher, and he would probably like his owner to come down to his level so that faces can be rubbed together.
When you are on a cat's level and he sniffs at your face and then rubs against you, sniff back, do not blow. Expelling air in your cat's face is the same as another cat hissing at it, and is seen as a very unfriendly gesture. A cat's sense of smell is much more developed than ours, and one of its uses is to identify other cats. With practice, we can distinguish between different cats by smell alone, too.
Cats living in one household develop a scent which is different from that of a group living in another household. And within their own household scent, each cat has his own individual scent. Most cat owners could probably identify their own cat just by sniffing at his nose.
Each breed of cat probably has his own scent, and it is possible that each color of cat may smell different. Certain breeds and certain colors of cat appear to get on better than do others. When cats greet each other they sniff faces first, then rub along one another's bodies and sniff at the base of the tail. From this, each can tell if the other is a cat they know, if he has been close to unfamiliar cats, where he has been, and what his sexual status is.
Often cats from the same household will hiss at a companion on his return from a visit to the vet because of the unfamiliar smell which still attaches to him. And if a human is invited to sniff back at a cat's face, which could be considered an honor, the cat will probably then turn his tail; this is also undoubtedly an invitation to sniff.
Grooming by licking not only settles the fur neatly and keeps it clean, it also gives it the right smell. As several cats in one household usually eat the same food, their saliva might be expected to smell similar, and this could help mark the fur with a scent familiar to all. Unfamiliar cats will be shown they are unwelcome by a range of behavior and language, beginning with the hiss.