This article might help us grasp this particular usage of the word "literacies":
Today, reading, reading instruction, and more broadly conceived notions of literacy and literacy instruction are being defined by change in even more profound ways as new technologies require new literacies to effectively exploit their potentials. These include technologies such as gaming software, video technologies, technologies that establish communities on the Internet, search, webpages, and many more yet to emerge.
So, basically, each literacy is some kind of a skill. A person good at using video technologies has a literacy in that particular area. Someone who knows how to search the Internet using various combinations of symbols and letters has acquired a literacy in this area. Does this make sense?
Student or Learner