This is one way cats show affection or try to get your attention. Not all cats do this, however, but they might show this in other ways such as as kneading, gentle scratching and gifting etc. Cats also show affection to other animals by rubbing against them
"When your cat puts its scent on you, it's saying something like, 'You and I belong together because I smell you on me and you smell me on you.' It's a scent complement."
Some cats periodically approach a relaxed owner and stretch out their paws to softly touch the owner's face. The cat repeats this gentle reaching in the hope that the owner will pet it, brush it or show some affection. Alternatively, some cats paw their owner's face to wake them from sleep; in this case the cat probably wants affection or play.