A build tool is a software application that automates the process of converting source code into executable programs. It manages tasks such as compiling code, linking libraries, and packaging files, making it easier for developers to create software efficiently. Common build tools include Maven, Gradle, and Ant, each offering different features and capabilities. Using a build tool helps ensure consistency and reduces the likelihood of errors during the development process. It allows developers to define project dependencies and configurations in a structured way, streamlining collaboration among team members. This automation saves time and improves productivity in software development projects.