If you're a genuine devotee of the kitty species, then you may be familiar with the concept of bunting -- when a cat bumps her head into you, whether your arm, face or anywhere else. If your kitty buries her face in your arm, she's basically giving you her scent.
If your cute kitty head-butts you, it isn't solely an act of friendship or love, although those components are definitely there too. According to ASPCA Professional, the act is aimed at marking you with a scent. Cats are territorial little creatures. Felines give off facial pheromones via scent glands on their cheeks. The oily emissions not only serve to claim you as her "property," they also soothe and relax your cat.
Your cat burying her head into you doesn't always mean that she's marking you, however. In some cases, the action can indicate a desire for attention. If your cutie buries her head into your arm and then immediately follows it with tilting her head and extending her neck out to you, it may mean that she wants you to give her some friendly scratches or strokes.
Although a cat marking you does often mean that she's marking you as her turf, the act isn't really a selfish one, at least not fully. By marking you with her face and head, your pet is trying to make sure you smell just like her. If you smell like your cat, you function as a source of comfort and familiarity to her. The more comforting your presence is to your cat, the more she'll adore you. A pretty sweet deal in a lot of ways.
If you notice your cat burrowing her head into another feline's head, she's probably doing the same thing that she does to your arm -- giving off her scent. However, cats also often bunt their close relatives as a happy greeting of sorts. When a cat bunts another, it's surely a sign of a close and trusting rapport. The urge to spread scent is by no means a hostile one. In fact, the cozy gesture is similar to a hug, in a way!