Docker and Docker-Compose concepts are two means in Linux by which a developer can easily generate a running container application from a docker image that is pulled down from a repository at GitHub, LinuxServer.io, or DockerHub, then access that running application in a Web browser at a particular port that is assigned to or configured for the application itself. This assignment is performed within a file called the docker-compose.yml file for docker-compose applications. The docker-compose.yml is short for docker-compose YAML file.