What is the difference between a Docker image and a Docker container?

A Docker image is a read-only template built from a Dockerfile. Think of it as a class definition. A container is a running instance of that image — a class instantiation. You can run many containers from the same image, each isolated from the others.

# Build an image
docker build -t my-app:1.0 .

# Run a container from that image
docker run -d -p 8080:80 my-app:1.0