Editing Docker (section)

== <span style="color: #FFFFFF;">Remembering</span> ==
Key terms:

* '''Container''' � a lightweight, isolated process that runs an application and its dependencies, sharing the host OS kernel.
* '''Image''' � a read-only snapshot that defines a container's filesystem and configuration. Running an image produces a container.
* '''Dockerfile''' � a text file of instructions used to build an image layer by layer.
* '''Docker Hub''' � the default public registry where images are stored and shared.
* '''Registry''' � a server that stores and serves Docker images (public: Docker Hub, GitHub Container Registry; private: AWS ECR, GCP Artifact Registry).
* '''Layer''' � each instruction in a Dockerfile produces a layer; layers are cached and reused across builds to speed up rebuilds.
* '''Volume''' � a mechanism for persisting data outside the container's ephemeral filesystem.
* '''Port mapping''' � connecting a port on the host machine to a port inside the container (e.g., -p 8080:80).
* '''Docker Compose''' � a tool for defining and running multi-container applications via a YAML file.
* '''Orchestration''' � managing multiple containers across multiple machines (Kubernetes is the dominant tool).

Distinction: a '''virtual machine''' runs a full OS on emulated hardware; a container shares the host kernel and is thus much lighter (~MB vs ~GB, seconds to start vs minutes).
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