Build tools are essential applications in software development that automate the process of compiling source code, linking libraries, and creating executable or deployable software artifacts. They enhance efficiency by managing dependencies, ensuring code consistency, and automating repetitive tasks, allowing developers to focus on writing code rather than manual compilation. Common build tools, such as Apache Maven and Gradle, streamline the build process and facilitate collaboration among development teams. By mechanizing mundane operations like testing and packaging, build tools significantly improve productivity and help maintain uniformity across different projects and environments, making them indispensable in modern software development.