I think it depends on your current relationship and history with the guy. If he is usually a hands on person who likes and hugs everyone then it is probably him being his usual self. Although if it's a guy that never hugs anyone it could mean he likes you!
It means he is hugging you. Isn't it that obvious? Can't a guy hug his love now without it being questioned? Typically, hugging from behind is a sign of protection, when a guy covers your back with his chest and holds your front with his arms, he is lovingly protecting you in a cuddle.