Containers are a technology that allows an application and all its dependencies to be packaged into an isolated and portable unit, ensuring that the software runs consistently in any environment. They function as lightweight "boxes" that isolate the application without the need to virtualize the entire operating system. This facilitates the deployment, scaling, and maintenance of applications, especially in microservices environments. Additionally, containers reduce conflicts between libraries and system configurations, accelerating development and continuous integration. Tools like Docker have popularized this technology, allowing development and operations teams to work more agilely and collaboratively. In summary, containers optimize resources and simplify the migration of applications between servers and clouds.