Reinforcement learning is not strictly what is considered supervised learning in ML, but it's very much in the same vein. And a supervised learning algorithm doesn't have any "knowledge" of the domain it's learning about either - it just adjusts its parameters based on training example and class/output pairs. RL attempts to find the best actions to take to ultimately maximize a measure cumulative reward, i.e. a signal which provides an objective measure of performance (much like the class or target output of a training example used in supervised learning).

RL is definitely not unsupervised learning, which in contrast, attempts to find some structure in unlabeled data.