SystemC is a set of C++ classes and macros that provide an event-driven simulation environment for modeling and designing complex systems. It allows engineers to create high-level abstractions of hardware and software components, enabling them to simulate and verify system behavior before actual implementation. Developed by Accellera, SystemC is widely used in the fields of electronic design automation (EDA) and system-on-chip (SoC) design. It supports various levels of abstraction, from high-level system modeling to detailed hardware description, making it a versatile tool for both hardware and software engineers in the design process.