Software engineering is the systematic application of engineering principles to the design, development, testing, and maintenance of software systems. It involves analyzing user requirements, planning solutions, writing efficient and maintainable code, and ensuring the software meets quality standards and performs reliably in real-world conditions. Software engineers use various tools, programming languages, and methodologies—such as Agile, DevOps, or Waterfall—to manage complex projects, collaborate in teams, and deliver secure, scalable, and user-friendly applications that solve real-world problems across various industries.