This paper presents several new insights into system software, which is one of the basic concepts in computing discipline, from three perspectives of essential features, characteristics of the times, and the future development trend. The first insight is that system software stems theoretically and technically from universal Turing machine and the idea of stored-program, with an essential feature of "manipulating the execution of a computing system". There are two typical manipulation modes:encoding and then loading, executing and controlling. The second insight is that software system is a kind of software, in the Internet age, providing substantial online services continuously, which lay the foundation for the newly emerged "software-as-a-service" paradigm. The final insight is about its development trend:system software will evolve online continuously. Driven by innovations of computing systems, integration of cyber and physical spaces, and intelligence technologies, system software will become the core of future software ecology.