What is the difference between an image and a container?

An image is a static template; a container is a running instance of that image with its own writable layer.

Docker Container Basics: Your First Container

Published March 18, 2026·Updated October 29, 2026·8 min read

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Introduction

Docker packages an application and its dependencies into a portable container. This tutorial introduces images, containers, and the everyday CLI workflow.

Prerequisites

Docker Desktop installed
Basic command line familiarity

Step-by-Step Guide

Step 1: Pull an image

Images are read-only templates used to create containers.

docker pull node:20-alpine

Step 2: Run a container

Start a container from an image and map a port to your host machine.

docker run -p 3000:3000 node:20-alpine

Step 3: Write a Dockerfile

Define your own image by describing build steps in a Dockerfile.

FROM node:20-alpine
WORKDIR /app
COPY . .
RUN npm install
CMD ["npm", "start"]

Step 4: Manage containers

List, stop, and remove containers using the Docker CLI.

docker ps
docker stop <container-id>
docker rm <container-id>

FAQs

What is the difference between an image and a container?: An image is a static template; a container is a running instance of that image with its own writable layer.

Summary

Once you're comfortable pulling images and running containers, the natural next step is orchestrating multiple containers with Docker Compose or Kubernetes.

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