A software stack is a collection of software components that work together to create a complete application or system. It typically includes an operating system, middleware, and application software, all of which interact to perform specific tasks. For example, a common software stack for web development might include Linux as the operating system, Apache as the web server, MySQL for the database, and PHP as the programming language. Each layer of the software stack serves a distinct purpose and communicates with the layers above and below it. This modular approach allows developers to build, maintain, and update applications more efficiently. By using established stacks, such as the MEAN stack (which includes MongoDB, Express.js, Angular, and Node.js), developers can leverage existing tools and frameworks to streamline their work.