You're right, Ms. Harder, in the sense that “social media” is not a defined term in the bill. Not every term is defined. Where a term isn't defined, it would be understood in relation to its ordinary meaning. In this instance, it was intentional to leave the term undefined, to be understood in terms of its ordinary meaning, so that the framework can continue to evolve over time.
My understanding of what it would be is an Internet-based service that allows individuals to share content with one another in a network. That's roughly how I would define social media off the cuff.