Fundamentals

docker build sends a directory to the Docker daemon, then executes your Dockerfile against it one cached layer at a time.

A VM virtualizes hardware and runs a full kernel per guest. A container shares the host kernel and isolates a process. That one difference explains almost everything else.

Linux runs Docker natively. Mac and Windows run it inside a small Linux VM, which is worth knowing before you chase a ‘missing’ performance number.

A Dockerfile is a build recipe: a short list of instructions that turns a base image and your files into a new image.