Why do guinea pigs lick your fingers and does it mean they are happy?

We use to rise them they do that to get the salt from your skin Well, I wouldn't say it means they are happy, it definitely means they are not scared. They wouldn't do that if they were at all uneasy, so it's a good thing! They also groom each other, so in addition to getting salt from your skin, they may just be grooming you or kissing you! They also lightly nibble sometimes. It means they have grown to like you