1. Images, containers, layers and registries

• Image — read-only template made of stacked layers (each Dockerfile instruction adds one). Identified by repository:tag (e.g. myacr.azurecr.io/shop-api:1.4.2) and an immutable digest (@sha256:...).
• Container — image + a thin writable layer + runtime config (env vars, ports, mounts). Changes in the writable layer are lost when the container is removed.
• Layer caching — unchanged layers are reused between builds and shared between images on disk (copy-on-write via the overlay2 storage driver).
• Registry — stores images; repository — one image name with many tags.

docker pull mcr.microsoft.com/dotnet/aspnet:10.0
docker images
docker run -d --name web -p 8080:8080 -e ASPNETCORE_ENVIRONMENT=Development shop-api:dev
docker ps -a
docker logs -f web
docker exec -it web /bin/sh          # shell inside (if the image has one)
docker stop web && docker rm web
docker image prune -a                 # remove unused images
docker system df                      # disk usage

Interview tip: never use the latest tag in production — use immutable version tags or digests so deployments are reproducible.