Containerization is a lightweight form of virtualization that allows developers to package an application and its dependencies into a single, isolated unit called a container. Containers share the host system's operating system kernel but run in their own isolated environment, which includes the application code, runtime, libraries, and configuration files. This ensures that the application runs consistently across different environments, whether it’s on a developer's local machine, a testing server, or in production.

Containers have become popular in modern software development due to their efficiency, portability, and scalability. Unlike traditional virtual machines, containers are much more lightweight because they don’t include a full operating system image, allowing for faster startup times and reduced resource usage. Tools like Docker and Kubernetes have become industry standards for managing containers, enabling organizations to deploy, manage, and scale applications more effectively in cloud environments. Containerization also facilitates microservices architecture, where applications are broken down into smaller, loosely coupled services that can be developed, deployed, and scaled independently.