A Docker image is a package containing everything required by an app to run.
sudo docker image pull redis:latest
sudo docker image ls
    # redis latest d2e4e1f51132 5.8MB

# Search Docker Hub
sudo docker search mongodb --filter "is-official=true"
    # mongo           MongoDB document databases provide high avai… 
    # mongo-express   Web-based MongoDB admin interface, written w… 
Use rmi to remove a Docker image.
docker rmi web.latest
    # Untagged: web.latest:latest
docker rmi test
    # Untagged: test:latest

docker image ls
    # REPOSITORY   TAG       IMAGE ID       CREATED        SIZE
    # web          latest    58188456312c   26 hours ago   81.9MB
    # alpine       latest    0ac33e5f5afa   4 weeks ago    5.57MB


Those are the main command related to managing docker images.
docker images

# You can remove one container image.
docker rmi IMAGE_ID

# If can force the deletion with -f flag
docker rmi -f 1df330ae0770

# You can list all containers, including stopped ones
docker ps -a

# You can remove stopped containers
docker rm CONTAINER_ID

# You can remove all stopped containers at once
docker container prune

# You can remove all Docker images at once by using the docker image prune command
docker image prune -a

# You can remove all images except for the latest tag
docker images -q -f "dangling=false" | xargs docker rmi -f 

  Last update: 121 days ago