The services section in a docker-compose file is an array of containers which are to be built and run together when the docker-compose file is executed. Each container under a docker-compose file is indicated with a user specific "service_name" which is used by other containers for communication among themselves. These "service names" need to be unique within a docker-compose file and are auto resolved for their respective containers by the docker.
version: '3' services: redis-server: build: . ports: - 8000:6379 angular-app: build: . ports: - 8080:80