The significance of a technology stack in development lies in its role as the combination of programming languages, frameworks, libraries, and tools used to build a web or mobile application. A well-chosen technology stack ensures compatibility, efficiency, and ease of maintenance throughout the development lifecycle. It influences the application's performance, scalability, and security. Additionally, the technology stack impacts team collaboration and productivity, as developers need expertise in the selected technologies. Understanding a technology stack helps guide decisions regarding future updates, integrations, and overall system architecture.