A container is a running instance of an image. You can create, start, stop, move, or delete a container using the Docker API or CLI. You can connect a container to one or more networks, attach storage to it, or even create a new image based on its current state. Basically, a container is a very lightweight VM that only provides the resources and environment to run applications.
FROM. The first instruction in the Dockerfile must beFROM, which defines the base image to use to start the build process. TheFROMinstruction can appear multiple times within a single Dockerfile in order to create multiple images. Simply make a note of the last image ID output by the commit before each newFROMinstruction.