Software architecture refers to the high-level structure of a software system, defining how different components interact and work together. It serves as a blueprint for both the system and the project developing it, outlining the organization of code, data flow, and the relationships between various parts. Good software architecture ensures that a system is scalable, maintainable, and efficient. It involves making key decisions about technology choices, design patterns, and frameworks, which can significantly impact the system's performance and adaptability to future changes.