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The power of containerized applications stems from their architecture, which leverages the host operating system's kernel while maintaining strict isolation.

1. The Container Image (The Blueprint): The application starts as a container image, an immutable file built from a set of instructions (a Dockerfile). This image contains a layered filesystem snapshot of the application and its environment.‍
2. The Container Runtime (The Engine): A container runtime (like containerd or CRI-0) is the software that pulls the image and creates a running container instance. It uses Linux kernel features like namespaces (for isolation) and cgroups (for resource limits) to create a secure, isolated environment for the application to run.‍
3. The Host OS (The Foundation): The container shares the host machine's operating system kernel but runs in its own isolated user space. This is what makes containers so much more lightweight than virtual machines (VMs), which require their own full guest OS.