What protocol is Spektrum?

Could you elaborate on the nature and functionality of the Spektrum protocol? I'm particularly interested in understanding its core principles and how it differs from other blockchain or cryptocurrency protocols. What are the key innovations and advantages that Spektrum brings to the market? Additionally, what are the main use cases or applications that Spektrum aims to enable? Finally, what challenges does Spektrum face in terms of adoption and scalability, and how does it plan to address these issues?