In software terms, a stack is a collection of technologies - including languages, libraries, databases, and tools - used together to create a web application. Each layer of technology in the stack supports the layers above it, forming a 'stack'.
For example, the LAMP stack consists of Linux as the operating system, Apache as the web server, MySQL as the database, and PHP as the programming language. Another popular example is the MEAN stack, which includes MongoDB for the database, Express.js as the web framework, Angular for the front-end framework, and Node.js for the server platform.
Choosing the right technology stack is crucial for project success. Factors to consider when choosing a stack include project requirements, team expertise, scalability needs, and the community and support surrounding the technologies.