Qsys is a powerful system integration tool that is included as part of the Quartus® Prime Standard Edition software. Qsys captures system-level hardware designs at a high level of abstraction and also automates the task of defining and integrating custom HDL design blocks, commonly referred to as design modules, IP cores, or components.
Qsys facilitates design reuse by packaging and making available your custom components and systems. You can use Qsys to integrate your own components with the components that Altera and third-party developers provide. In some cases, you can implement an entire design using components from the Altera component library.
During system generation, Qsys automatically creates high-performance interconnect logic from the connectivity you specify, eliminating the error-prone and time-consuming task of writing HDL to specify the system-level connections.