Custom web application development involves creating tailored web solutions to meet specific business needs. It includes planning, design, development, testing, and deployment using technologies like JavaScript, Python, and React. Custom web apps offer flexibility, scalability, and seamless integration for enhanced functionality and security. They provide businesses with a competitive edge by optimizing workflows, improving user experience, and ensuring better performance. Additionally, they can be designed to handle high traffic, support multiple devices, and integrate with third-party services for greater efficiency.