A cat licking your arm may mean many things. Generally speaking, cats licking people is an intimate behavior. They may express their love and closeness to you in this way. Among cats' social behaviors, licking is often a friendly form of communication, similar to a kiss or hug in humans.

Cats are naturally clean animals and they will often lick their fur to keep it clean. Sometimes, they may extend this behavior to humans, especially if you smell like something they like.