Capistrano is an open-source tool used for automating the deployment of web applications. It simplifies the process of transferring files, running commands, and managing server configurations, making it easier for developers to deploy their code to production environments. Originally designed for Ruby on Rails applications, Capistrano has since expanded to support various programming languages and frameworks. It uses a simple configuration file to define tasks and can be customized to fit different deployment workflows, enhancing efficiency and reducing the risk of errors during the deployment process.